diff --git a/.golangci.yml b/.golangci.yml
index 2c80f690b..089f935dc 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -24,7 +24,8 @@ linters:
     - exportloopref
     - goconst
     - goimports
-    - gofmt
+    - gofmt # redundant, since gofmt *should* be a no-op after gofumpt
+    - gofumpt
     - gosimple
     - ineffassign
     - misspell
diff --git a/benchmark/benchmark_suite_test.go b/benchmark/benchmark_suite_test.go
index 26df5f92c..d23344293 100644
--- a/benchmark/benchmark_suite_test.go
+++ b/benchmark/benchmark_suite_test.go
@@ -3,11 +3,10 @@ package benchmark
 import (
 	"flag"
 	"math/rand"
+	"testing"
 
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
-
-	"testing"
 )
 
 func TestBenchmark(t *testing.T) {
@@ -15,9 +14,7 @@ func TestBenchmark(t *testing.T) {
 	RunSpecs(t, "Benchmark Suite")
 }
 
-var (
-	size int // file size in MB, will be read from flags
-)
+var size int // file size in MB, will be read from flags
 
 func init() {
 	flag.IntVar(&size, "size", 50, "data length (in MB)")
diff --git a/conn_id_manager_test.go b/conn_id_manager_test.go
index 9690c6c0c..76e2b4ae5 100644
--- a/conn_id_manager_test.go
+++ b/conn_id_manager_test.go
@@ -243,7 +243,6 @@ var _ = Describe("Connection ID Manager", func() {
 			StatelessResetToken: protocol.StatelessResetToken{16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1},
 		})).To(Succeed())
 		Expect(m.Get()).To(Equal(protocol.ConnectionID{1, 2, 3, 4}))
-
 	})
 
 	It("initiates subsequent updates when enough packets are sent", func() {
diff --git a/crypto_stream_test.go b/crypto_stream_test.go
index a4d39014c..a4f92b65e 100644
--- a/crypto_stream_test.go
+++ b/crypto_stream_test.go
@@ -22,9 +22,7 @@ func createHandshakeMessage(len int) []byte {
 }
 
 var _ = Describe("Crypto Stream", func() {
-	var (
-		str cryptoStream
-	)
+	var str cryptoStream
 
 	BeforeEach(func() {
 		str = newCryptoStream()
diff --git a/fuzzing/handshake/fuzz.go b/fuzzing/handshake/fuzz.go
index bf068183d..0d49b813f 100644
--- a/fuzzing/handshake/fuzz.go
+++ b/fuzzing/handshake/fuzz.go
@@ -21,9 +21,11 @@ import (
 	"github.com/lucas-clemente/quic-go/internal/wire"
 )
 
-var cert, clientCert *tls.Certificate
-var certPool, clientCertPool *x509.CertPool
-var sessionTicketKey = [32]byte{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32}
+var (
+	cert, clientCert         *tls.Certificate
+	certPool, clientCertPool *x509.CertPool
+	sessionTicketKey         = [32]byte{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32}
+)
 
 func init() {
 	priv, err := rsa.GenerateKey(rand.Reader, 1024)
@@ -183,6 +185,7 @@ func (r *runner) OnError(err error) {
 	(*r.client).Close()
 	(*r.server).Close()
 }
+
 func (r *runner) Errored() bool {
 	r.Lock()
 	defer r.Unlock()
@@ -190,8 +193,10 @@ func (r *runner) Errored() bool {
 }
 func (r *runner) DropKeys(protocol.EncryptionLevel) {}
 
-const alpn = "fuzzing"
-const alpnWrong = "wrong"
+const (
+	alpn      = "fuzzing"
+	alpnWrong = "wrong"
+)
 
 func toEncryptionLevel(n uint8) protocol.EncryptionLevel {
 	switch n % 3 {
@@ -238,8 +243,10 @@ func getTransportParameters(seed uint8) *wire.TransportParameters {
 }
 
 // PrefixLen is the number of bytes used for configuration
-const PrefixLen = 12
-const confLen = 5
+const (
+	PrefixLen = 12
+	confLen   = 5
+)
 
 // Fuzz fuzzes the TLS 1.3 handshake used by QUIC.
 //go:generate go run ./cmd/corpus.go
diff --git a/fuzzing/internal/helper/helper.go b/fuzzing/internal/helper/helper.go
index b4a4ed328..c62118203 100644
--- a/fuzzing/internal/helper/helper.go
+++ b/fuzzing/internal/helper/helper.go
@@ -33,7 +33,7 @@ func WriteCorpusFile(path string, data []byte) error {
 		}
 	}
 	hash := sha1.Sum(data)
-	return ioutil.WriteFile(filepath.Join(path, hex.EncodeToString(hash[:])), data, 0644)
+	return ioutil.WriteFile(filepath.Join(path, hex.EncodeToString(hash[:])), data, 0o644)
 }
 
 // WriteCorpusFileWithPrefix writes data to a corpus file in directory path.
diff --git a/http3/client.go b/http3/client.go
index 3a5df2552..bf850c0ea 100644
--- a/http3/client.go
+++ b/http3/client.go
@@ -19,8 +19,10 @@ import (
 // Note that 0-RTT data doesn't provide replay protection.
 const MethodGet0RTT = "GET_0RTT"
 
-const defaultUserAgent = "quic-go HTTP/3"
-const defaultMaxResponseHeaderBytes = 10 * 1 << 20 // 10 MB
+const (
+	defaultUserAgent              = "quic-go HTTP/3"
+	defaultMaxResponseHeaderBytes = 10 * 1 << 20 // 10 MB
+)
 
 var defaultQuicConfig = &quic.Config{
 	MaxIncomingStreams: -1, // don't allow the server to create bidirectional streams
diff --git a/http3/response_writer.go b/http3/response_writer.go
index 8f4d69604..3288e4cb6 100644
--- a/http3/response_writer.go
+++ b/http3/response_writer.go
@@ -22,8 +22,10 @@ type responseWriter struct {
 	logger utils.Logger
 }
 
-var _ http.ResponseWriter = &responseWriter{}
-var _ http.Flusher = &responseWriter{}
+var (
+	_ http.ResponseWriter = &responseWriter{}
+	_ http.Flusher        = &responseWriter{}
+)
 
 func newResponseWriter(stream io.Writer, logger utils.Logger) *responseWriter {
 	return &responseWriter{
diff --git a/http3/roundtrip_test.go b/http3/roundtrip_test.go
index 0f357412a..aa136952d 100644
--- a/http3/roundtrip_test.go
+++ b/http3/roundtrip_test.go
@@ -23,6 +23,7 @@ type mockClient struct {
 func (m *mockClient) RoundTrip(req *http.Request) (*http.Response, error) {
 	return &http.Response{Request: req}, nil
 }
+
 func (m *mockClient) Close() error {
 	m.closed = true
 	return nil
diff --git a/http3/server.go b/http3/server.go
index be4417980..5e755297d 100644
--- a/http3/server.go
+++ b/http3/server.go
@@ -35,13 +35,11 @@ type contextKey struct {
 
 func (k *contextKey) String() string { return "quic-go/http3 context value " + k.name }
 
-var (
-	// ServerContextKey is a context key. It can be used in HTTP
-	// handlers with Context.Value to access the server that
-	// started the handler. The associated value will be of
-	// type *http3.Server.
-	ServerContextKey = &contextKey{"http3-server"}
-)
+// ServerContextKey is a context key. It can be used in HTTP
+// handlers with Context.Value to access the server that
+// started the handler. The associated value will be of
+// type *http3.Server.
+var ServerContextKey = &contextKey{"http3-server"}
 
 type requestError struct {
 	err       error
diff --git a/integrationtests/self/handshake_test.go b/integrationtests/self/handshake_test.go
index 0b9c92627..d1c5a9693 100644
--- a/integrationtests/self/handshake_test.go
+++ b/integrationtests/self/handshake_test.go
@@ -356,7 +356,6 @@ var _ = Describe("Handshake tests", func() {
 			Expect(err).To(HaveOccurred())
 			Expect(err.(*qerr.QuicError).ErrorCode).To(Equal(qerr.ConnectionRefused))
 		})
-
 	})
 
 	Context("ALPN", func() {
diff --git a/integrationtests/self/key_update_test.go b/integrationtests/self/key_update_test.go
index bb061a768..54317d04b 100644
--- a/integrationtests/self/key_update_test.go
+++ b/integrationtests/self/key_update_test.go
@@ -16,8 +16,10 @@ import (
 	. "github.com/onsi/gomega"
 )
 
-var sentHeaders []*logging.ExtendedHeader
-var receivedHeaders []*logging.ExtendedHeader
+var (
+	sentHeaders     []*logging.ExtendedHeader
+	receivedHeaders []*logging.ExtendedHeader
+)
 
 func countKeyPhases() (sent, received int) {
 	lastKeyPhase := protocol.KeyPhaseOne
@@ -75,6 +77,7 @@ func (t *connTracer) BufferedPacket(logging.PacketType)
 func (t *connTracer) DroppedPacket(logging.PacketType, logging.ByteCount, logging.PacketDropReason) {}
 func (t *connTracer) UpdatedMetrics(rttStats *logging.RTTStats, cwnd, bytesInFlight logging.ByteCount, packetsInFlight int) {
 }
+
 func (t *connTracer) LostPacket(logging.EncryptionLevel, logging.PacketNumber, logging.PacketLossReason) {
 }
 func (t *connTracer) UpdatedCongestionState(logging.CongestionState)                     {}
diff --git a/integrationtests/tools/proxy/proxy_suite_test.go b/integrationtests/tools/proxy/proxy_suite_test.go
index 6e413a82f..dd07db3b7 100644
--- a/integrationtests/tools/proxy/proxy_suite_test.go
+++ b/integrationtests/tools/proxy/proxy_suite_test.go
@@ -1,10 +1,10 @@
 package quicproxy
 
 import (
+	"testing"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
-
-	"testing"
 )
 
 func TestQuicGo(t *testing.T) {
diff --git a/internal/ackhandler/ackhandler_suite_test.go b/internal/ackhandler/ackhandler_suite_test.go
index 9e7e07776..734d6f48e 100644
--- a/internal/ackhandler/ackhandler_suite_test.go
+++ b/internal/ackhandler/ackhandler_suite_test.go
@@ -1,11 +1,11 @@
 package ackhandler
 
 import (
+	"testing"
+
 	"github.com/golang/mock/gomock"
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
-
-	"testing"
 )
 
 func TestCrypto(t *testing.T) {
diff --git a/internal/ackhandler/received_packet_history_test.go b/internal/ackhandler/received_packet_history_test.go
index 6c48a70e8..8054e1a23 100644
--- a/internal/ackhandler/received_packet_history_test.go
+++ b/internal/ackhandler/received_packet_history_test.go
@@ -9,9 +9,7 @@ import (
 )
 
 var _ = Describe("receivedPacketHistory", func() {
-	var (
-		hist *receivedPacketHistory
-	)
+	var hist *receivedPacketHistory
 
 	BeforeEach(func() {
 		hist = newReceivedPacketHistory()
diff --git a/internal/ackhandler/sent_packet_handler.go b/internal/ackhandler/sent_packet_handler.go
index cb34f57d8..9f5486472 100644
--- a/internal/ackhandler/sent_packet_handler.go
+++ b/internal/ackhandler/sent_packet_handler.go
@@ -88,8 +88,10 @@ type sentPacketHandler struct {
 	logger        utils.Logger
 }
 
-var _ SentPacketHandler = &sentPacketHandler{}
-var _ sentPacketTracker = &sentPacketHandler{}
+var (
+	_ SentPacketHandler = &sentPacketHandler{}
+	_ sentPacketTracker = &sentPacketHandler{}
+)
 
 func newSentPacketHandler(
 	initialPacketNumber protocol.PacketNumber,
diff --git a/internal/ackhandler/sent_packet_handler_test.go b/internal/ackhandler/sent_packet_handler_test.go
index 9f3a1a765..338144072 100644
--- a/internal/ackhandler/sent_packet_handler_test.go
+++ b/internal/ackhandler/sent_packet_handler_test.go
@@ -232,10 +232,11 @@ var _ = Describe("SentPacketHandler", func() {
 				ping := &wire.PingFrame{}
 				handler.SentPacket(ackElicitingPacket(&Packet{
 					PacketNumber: 13,
-					Frames: []Frame{{Frame: ping, OnAcked: func(f wire.Frame) {
-						Expect(f).To(Equal(ping))
-						acked = true
-					},
+					Frames: []Frame{{
+						Frame: ping, OnAcked: func(f wire.Frame) {
+							Expect(f).To(Equal(ping))
+							acked = true
+						},
 					}},
 				}))
 				ack := &wire.AckFrame{AckRanges: []wire.AckRange{{Smallest: 13, Largest: 13}}}
diff --git a/internal/congestion/congestion_suite_test.go b/internal/congestion/congestion_suite_test.go
index 577ee5bf7..6a0f7ed7a 100644
--- a/internal/congestion/congestion_suite_test.go
+++ b/internal/congestion/congestion_suite_test.go
@@ -1,10 +1,10 @@
 package congestion
 
 import (
+	"testing"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
-
-	"testing"
 )
 
 func TestCongestion(t *testing.T) {
diff --git a/internal/congestion/cubic.go b/internal/congestion/cubic.go
index 5e0139849..392ec7b81 100644
--- a/internal/congestion/cubic.go
+++ b/internal/congestion/cubic.go
@@ -17,9 +17,11 @@ import (
 
 // 1024*1024^3 (first 1024 is from 0.100^3)
 // where 0.100 is 100 ms which is the scaling round trip time.
-const cubeScale = 40
-const cubeCongestionWindowScale = 410
-const cubeFactor protocol.ByteCount = 1 << cubeScale / cubeCongestionWindowScale / maxDatagramSize
+const (
+	cubeScale                                    = 40
+	cubeCongestionWindowScale                    = 410
+	cubeFactor                protocol.ByteCount = 1 << cubeScale / cubeCongestionWindowScale / maxDatagramSize
+)
 
 const defaultNumConnections = 1
 
diff --git a/internal/congestion/cubic_sender.go b/internal/congestion/cubic_sender.go
index 936fb4cc5..7c5ee3b0d 100644
--- a/internal/congestion/cubic_sender.go
+++ b/internal/congestion/cubic_sender.go
@@ -63,8 +63,10 @@ type cubicSender struct {
 	tracer    logging.ConnectionTracer
 }
 
-var _ SendAlgorithm = &cubicSender{}
-var _ SendAlgorithmWithDebugInfos = &cubicSender{}
+var (
+	_ SendAlgorithm               = &cubicSender{}
+	_ SendAlgorithmWithDebugInfos = &cubicSender{}
+)
 
 // NewCubicSender makes a new cubic sender
 func NewCubicSender(clock Clock, rttStats *utils.RTTStats, reno bool, tracer logging.ConnectionTracer) *cubicSender {
diff --git a/internal/congestion/cubic_sender_test.go b/internal/congestion/cubic_sender_test.go
index b341ee7a3..83b4a7002 100644
--- a/internal/congestion/cubic_sender_test.go
+++ b/internal/congestion/cubic_sender_test.go
@@ -9,8 +9,10 @@ import (
 	. "github.com/onsi/gomega"
 )
 
-const initialCongestionWindowPackets = 10
-const defaultWindowTCP = protocol.ByteCount(initialCongestionWindowPackets) * maxDatagramSize
+const (
+	initialCongestionWindowPackets = 10
+	defaultWindowTCP               = protocol.ByteCount(initialCongestionWindowPackets) * maxDatagramSize
+)
 
 type mockClock time.Time
 
diff --git a/internal/congestion/cubic_test.go b/internal/congestion/cubic_test.go
index eb3b5bedd..390a14884 100644
--- a/internal/congestion/cubic_test.go
+++ b/internal/congestion/cubic_test.go
@@ -9,11 +9,13 @@ import (
 	. "github.com/onsi/gomega"
 )
 
-const numConnections uint32 = 2
-const nConnectionBeta float32 = (float32(numConnections) - 1 + beta) / float32(numConnections)
-const nConnectionBetaLastMax float32 = (float32(numConnections) - 1 + betaLastMax) / float32(numConnections)
-const nConnectionAlpha float32 = 3 * float32(numConnections) * float32(numConnections) * (1 - nConnectionBeta) / (1 + nConnectionBeta)
-const maxCubicTimeInterval = 30 * time.Millisecond
+const (
+	numConnections         uint32  = 2
+	nConnectionBeta        float32 = (float32(numConnections) - 1 + beta) / float32(numConnections)
+	nConnectionBetaLastMax float32 = (float32(numConnections) - 1 + betaLastMax) / float32(numConnections)
+	nConnectionAlpha       float32 = 3 * float32(numConnections) * float32(numConnections) * (1 - nConnectionBeta) / (1 + nConnectionBeta)
+	maxCubicTimeInterval           = 30 * time.Millisecond
+)
 
 var _ = Describe("Cubic", func() {
 	var (
diff --git a/internal/congestion/hybrid_slow_start.go b/internal/congestion/hybrid_slow_start.go
index f41c1e5c3..b5ae3d5eb 100644
--- a/internal/congestion/hybrid_slow_start.go
+++ b/internal/congestion/hybrid_slow_start.go
@@ -17,8 +17,10 @@ const hybridStartMinSamples = uint32(8)
 // Exit slow start if the min rtt has increased by more than 1/8th.
 const hybridStartDelayFactorExp = 3 // 2^3 = 8
 // The original paper specifies 2 and 8ms, but those have changed over time.
-const hybridStartDelayMinThresholdUs = int64(4000)
-const hybridStartDelayMaxThresholdUs = int64(16000)
+const (
+	hybridStartDelayMinThresholdUs = int64(4000)
+	hybridStartDelayMaxThresholdUs = int64(16000)
+)
 
 // HybridSlowStart implements the TCP hybrid slow start algorithm
 type HybridSlowStart struct {
diff --git a/internal/congestion/hybrid_slow_start_test.go b/internal/congestion/hybrid_slow_start_test.go
index fee8945e2..4b947db64 100644
--- a/internal/congestion/hybrid_slow_start_test.go
+++ b/internal/congestion/hybrid_slow_start_test.go
@@ -9,9 +9,7 @@ import (
 )
 
 var _ = Describe("Hybrid slow start", func() {
-	var (
-		slowStart HybridSlowStart
-	)
+	var slowStart HybridSlowStart
 
 	BeforeEach(func() {
 		slowStart = HybridSlowStart{}
@@ -71,5 +69,4 @@ var _ = Describe("Hybrid slow start", func() {
 		// RTT provided.
 		Expect(slowStart.ShouldExitSlowStart(rtt+10*time.Millisecond, rtt, 100)).To(BeTrue())
 	})
-
 })
diff --git a/internal/flowcontrol/flowcontrol_suite_test.go b/internal/flowcontrol/flowcontrol_suite_test.go
index 16da9ed26..6a325b423 100644
--- a/internal/flowcontrol/flowcontrol_suite_test.go
+++ b/internal/flowcontrol/flowcontrol_suite_test.go
@@ -1,11 +1,11 @@
 package flowcontrol
 
 import (
+	"testing"
+
 	"github.com/golang/mock/gomock"
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
-
-	"testing"
 )
 
 func TestCrypto(t *testing.T) {
diff --git a/internal/handshake/crypto_setup.go b/internal/handshake/crypto_setup.go
index aa8b2cd1f..3107fffb9 100644
--- a/internal/handshake/crypto_setup.go
+++ b/internal/handshake/crypto_setup.go
@@ -137,8 +137,10 @@ type cryptoSetup struct {
 	has1RTTOpener bool
 }
 
-var _ qtls.RecordLayer = &cryptoSetup{}
-var _ CryptoSetup = &cryptoSetup{}
+var (
+	_ qtls.RecordLayer = &cryptoSetup{}
+	_ CryptoSetup      = &cryptoSetup{}
+)
 
 // NewCryptoSetupClient creates a new crypto setup for the client
 func NewCryptoSetupClient(
diff --git a/internal/handshake/handshake_suite_test.go b/internal/handshake/handshake_suite_test.go
index 807b4afe3..1c763b760 100644
--- a/internal/handshake/handshake_suite_test.go
+++ b/internal/handshake/handshake_suite_test.go
@@ -4,6 +4,7 @@ import (
 	"crypto/tls"
 	"encoding/hex"
 	"strings"
+	"testing"
 
 	"github.com/lucas-clemente/quic-go/internal/qtls"
 
@@ -11,8 +12,6 @@ import (
 
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
-
-	"testing"
 )
 
 func TestHandshake(t *testing.T) {
diff --git a/internal/handshake/header_protector.go b/internal/handshake/header_protector.go
index 309af6b18..e1c72c3b6 100644
--- a/internal/handshake/header_protector.go
+++ b/internal/handshake/header_protector.go
@@ -26,7 +26,6 @@ func newHeaderProtector(suite *qtls.CipherSuiteTLS13, trafficSecret []byte, isLo
 	default:
 		panic(fmt.Sprintf("Invalid cipher suite id: %d", suite.ID))
 	}
-
 }
 
 type aesHeaderProtector struct {
diff --git a/internal/handshake/retry.go b/internal/handshake/retry.go
index b589b9911..30be193c3 100644
--- a/internal/handshake/retry.go
+++ b/internal/handshake/retry.go
@@ -13,7 +13,7 @@ import (
 var retryAEAD cipher.AEAD
 
 func init() {
-	var key = [16]byte{0xcc, 0xce, 0x18, 0x7e, 0xd0, 0x9a, 0x09, 0xd0, 0x57, 0x28, 0x15, 0x5a, 0x6c, 0xb9, 0x6b, 0xe1}
+	key := [16]byte{0xcc, 0xce, 0x18, 0x7e, 0xd0, 0x9a, 0x09, 0xd0, 0x57, 0x28, 0x15, 0x5a, 0x6c, 0xb9, 0x6b, 0xe1}
 
 	aes, err := aes.NewCipher(key[:])
 	if err != nil {
@@ -26,9 +26,11 @@ func init() {
 	retryAEAD = aead
 }
 
-var retryBuf bytes.Buffer
-var retryMutex sync.Mutex
-var retryNonce = [12]byte{0xe5, 0x49, 0x30, 0xf9, 0x7f, 0x21, 0x36, 0xf0, 0x53, 0x0a, 0x8c, 0x1c}
+var (
+	retryBuf   bytes.Buffer
+	retryMutex sync.Mutex
+	retryNonce = [12]byte{0xe5, 0x49, 0x30, 0xf9, 0x7f, 0x21, 0x36, 0xf0, 0x53, 0x0a, 0x8c, 0x1c}
+)
 
 // GetRetryIntegrityTag calculates the integrity tag on a Retry packet
 func GetRetryIntegrityTag(retry []byte, origDestConnID protocol.ConnectionID) *[16]byte {
diff --git a/internal/handshake/updatable_aead.go b/internal/handshake/updatable_aead.go
index 67247ae0c..fb3ae9a35 100644
--- a/internal/handshake/updatable_aead.go
+++ b/internal/handshake/updatable_aead.go
@@ -61,8 +61,10 @@ type updatableAEAD struct {
 	nonceBuf []byte
 }
 
-var _ ShortHeaderOpener = &updatableAEAD{}
-var _ ShortHeaderSealer = &updatableAEAD{}
+var (
+	_ ShortHeaderOpener = &updatableAEAD{}
+	_ ShortHeaderSealer = &updatableAEAD{}
+)
 
 func newUpdatableAEAD(rttStats *utils.RTTStats, tracer logging.ConnectionTracer, logger utils.Logger) *updatableAEAD {
 	return &updatableAEAD{
diff --git a/internal/protocol/protocol_suite_test.go b/internal/protocol/protocol_suite_test.go
index 204a3680e..60da0157a 100644
--- a/internal/protocol/protocol_suite_test.go
+++ b/internal/protocol/protocol_suite_test.go
@@ -1,10 +1,10 @@
 package protocol
 
 import (
+	"testing"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
-
-	"testing"
 )
 
 func TestProtocol(t *testing.T) {
diff --git a/internal/protocol/stream.go b/internal/protocol/stream.go
index 988dcc82f..ad7de864b 100644
--- a/internal/protocol/stream.go
+++ b/internal/protocol/stream.go
@@ -61,7 +61,7 @@ func (s StreamID) InitiatedBy() Perspective {
 	return PerspectiveServer
 }
 
-//Type says if this is a unidirectional or bidirectional stream
+// Type says if this is a unidirectional or bidirectional stream
 func (s StreamID) Type() StreamType {
 	if s%4 >= 2 {
 		return StreamTypeUni
diff --git a/internal/qerr/quic_error_test.go b/internal/qerr/quic_error_test.go
index a984e1867..4d547287a 100644
--- a/internal/qerr/quic_error_test.go
+++ b/internal/qerr/quic_error_test.go
@@ -52,7 +52,6 @@ var _ = Describe("QUIC Transport Errors", func() {
 			err := NewCryptoError(42, "")
 			Expect(err.IsCryptoError()).To(BeTrue())
 			Expect(err.IsApplicationError()).To(BeFalse())
-
 		})
 	})
 
diff --git a/internal/utils/rtt_stats_test.go b/internal/utils/rtt_stats_test.go
index 7a29518cf..1be304308 100644
--- a/internal/utils/rtt_stats_test.go
+++ b/internal/utils/rtt_stats_test.go
@@ -10,9 +10,7 @@ import (
 )
 
 var _ = Describe("RTT stats", func() {
-	var (
-		rttStats *RTTStats
-	)
+	var rttStats *RTTStats
 
 	BeforeEach(func() {
 		rttStats = NewRTTStats()
diff --git a/internal/utils/utils_suite_test.go b/internal/utils/utils_suite_test.go
index 2874819b8..9ecb8c052 100644
--- a/internal/utils/utils_suite_test.go
+++ b/internal/utils/utils_suite_test.go
@@ -1,10 +1,10 @@
 package utils
 
 import (
+	"testing"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
-
-	"testing"
 )
 
 func TestCrypto(t *testing.T) {
diff --git a/internal/wire/ack_frame_test.go b/internal/wire/ack_frame_test.go
index 1d9f37708..15c0f00ba 100644
--- a/internal/wire/ack_frame_test.go
+++ b/internal/wire/ack_frame_test.go
@@ -197,7 +197,6 @@ var _ = Describe("ACK Frame (for IETF QUIC)", func() {
 					Expect(err).To(MatchError(io.EOF))
 				}
 			})
-
 		})
 	})
 
diff --git a/internal/wire/log_test.go b/internal/wire/log_test.go
index 92874d24c..03f89dc18 100644
--- a/internal/wire/log_test.go
+++ b/internal/wire/log_test.go
@@ -53,7 +53,6 @@ var _ = Describe("Frame logging", func() {
 		}
 		LogFrame(logger, frame, false)
 		Expect(buf.String()).To(ContainSubstring("\t<- &wire.CryptoFrame{Offset: 42, Data length: 123, Offset + Data length: 165}\n"))
-
 	})
 
 	It("logs STREAM frames", func() {
diff --git a/internal/wire/max_data_frame.go b/internal/wire/max_data_frame.go
index 4fd9a1b1c..e6496d886 100644
--- a/internal/wire/max_data_frame.go
+++ b/internal/wire/max_data_frame.go
@@ -27,7 +27,7 @@ func parseMaxDataFrame(r *bytes.Reader, _ protocol.VersionNumber) (*MaxDataFrame
 	return frame, nil
 }
 
-//Write writes a MAX_STREAM_DATA frame
+// Write writes a MAX_STREAM_DATA frame
 func (f *MaxDataFrame) Write(b *bytes.Buffer, version protocol.VersionNumber) error {
 	b.WriteByte(0x10)
 	utils.WriteVarInt(b, uint64(f.MaximumData))
diff --git a/internal/wire/transport_parameters.go b/internal/wire/transport_parameters.go
index d8cf5177b..1f81eb23f 100644
--- a/internal/wire/transport_parameters.go
+++ b/internal/wire/transport_parameters.go
@@ -315,7 +315,7 @@ func (p *TransportParameters) readNumericTransportParameter(
 func (p *TransportParameters) Marshal(pers protocol.Perspective) []byte {
 	b := &bytes.Buffer{}
 
-	//add a greased value
+	// add a greased value
 	utils.WriteVarInt(b, uint64(27+31*rand.Intn(100)))
 	length := rand.Intn(16)
 	randomData := make([]byte, length)
diff --git a/internal/wire/wire_suite_test.go b/internal/wire/wire_suite_test.go
index f3b11d417..cc23c18b8 100644
--- a/internal/wire/wire_suite_test.go
+++ b/internal/wire/wire_suite_test.go
@@ -2,13 +2,12 @@ package wire
 
 import (
 	"bytes"
+	"testing"
 
 	"github.com/lucas-clemente/quic-go/internal/protocol"
 	"github.com/lucas-clemente/quic-go/internal/utils"
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
-
-	"testing"
 )
 
 func TestWire(t *testing.T) {
diff --git a/interop/utils/logging.go b/interop/utils/logging.go
index 623ec2129..4c35c9741 100644
--- a/interop/utils/logging.go
+++ b/interop/utils/logging.go
@@ -33,7 +33,7 @@ func GetQLOGWriter() (func(perspective logging.Perspective, connID []byte) io.Wr
 		return nil, nil
 	}
 	if _, err := os.Stat(qlogDir); os.IsNotExist(err) {
-		if err := os.MkdirAll(qlogDir, 0666); err != nil {
+		if err := os.MkdirAll(qlogDir, 0o666); err != nil {
 			return nil, fmt.Errorf("failed to create qlog dir %s: %s", qlogDir, err.Error())
 		}
 	}
diff --git a/metrics/metrics.go b/metrics/metrics.go
index e9bdac5d4..070ccc13e 100644
--- a/metrics/metrics.go
+++ b/metrics/metrics.go
@@ -196,6 +196,7 @@ func (t *connTracer) LostPacket(encLevel logging.EncryptionLevel, _ logging.Pack
 		lostPackets.M(1),
 	)
 }
+
 func (t *connTracer) UpdatedPTOCount(value uint32) {
 	if value == 0 {
 		return
diff --git a/qlog/qlog.go b/qlog/qlog.go
index 7c0134123..a394c6bd3 100644
--- a/qlog/qlog.go
+++ b/qlog/qlog.go
@@ -89,7 +89,8 @@ func (t *connectionTracer) run() {
 				},
 				EventFields: eventFields[:],
 			},
-		}}
+		},
+	}
 	if err := enc.Encode(tl); err != nil {
 		panic(fmt.Sprintf("qlog encoding into a bytes.Buffer failed: %s", err))
 	}
diff --git a/quic_suite_test.go b/quic_suite_test.go
index 1798fff7d..a26b35046 100644
--- a/quic_suite_test.go
+++ b/quic_suite_test.go
@@ -2,12 +2,11 @@ package quic
 
 import (
 	"sync"
+	"testing"
 
 	"github.com/golang/mock/gomock"
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
-
-	"testing"
 )
 
 func TestQuicGo(t *testing.T) {
diff --git a/receive_stream.go b/receive_stream.go
index a92baba1f..63b141bc1 100644
--- a/receive_stream.go
+++ b/receive_stream.go
@@ -52,8 +52,10 @@ type receiveStream struct {
 	version        protocol.VersionNumber
 }
 
-var _ ReceiveStream = &receiveStream{}
-var _ receiveStreamI = &receiveStream{}
+var (
+	_ ReceiveStream  = &receiveStream{}
+	_ receiveStreamI = &receiveStream{}
+)
 
 func newReceiveStream(
 	streamID protocol.StreamID,
diff --git a/send_stream.go b/send_stream.go
index 7fc3194e7..cb7a828df 100644
--- a/send_stream.go
+++ b/send_stream.go
@@ -57,8 +57,10 @@ type sendStream struct {
 	version protocol.VersionNumber
 }
 
-var _ SendStream = &sendStream{}
-var _ sendStreamI = &sendStream{}
+var (
+	_ SendStream  = &sendStream{}
+	_ sendStreamI = &sendStream{}
+)
 
 func newSendStream(
 	streamID protocol.StreamID,
diff --git a/server.go b/server.go
index b62fe73f4..29cbed672 100644
--- a/server.go
+++ b/server.go
@@ -103,8 +103,10 @@ type baseServer struct {
 	logger utils.Logger
 }
 
-var _ Listener = &baseServer{}
-var _ unknownPacketHandler = &baseServer{}
+var (
+	_ Listener             = &baseServer{}
+	_ unknownPacketHandler = &baseServer{}
+)
 
 type earlyServer struct{ *baseServer }
 
diff --git a/session.go b/session.go
index 3f8ff2775..5bede9e6d 100644
--- a/session.go
+++ b/session.go
@@ -213,9 +213,11 @@ type session struct {
 	logger utils.Logger
 }
 
-var _ Session = &session{}
-var _ EarlySession = &session{}
-var _ streamSender = &session{}
+var (
+	_ Session      = &session{}
+	_ EarlySession = &session{}
+	_ streamSender = &session{}
+)
 
 var newSession = func(
 	conn sendConn,
diff --git a/session_test.go b/session_test.go
index 83e2bf717..805cf4614 100644
--- a/session_test.go
+++ b/session_test.go
@@ -2701,6 +2701,5 @@ var _ = Describe("Client Session", func() {
 			tracer.EXPECT().DroppedPacket(gomock.Any(), gomock.Any(), gomock.Any())
 			Expect(sess.handlePacketImpl(wrapPacket(initialPacket))).To(BeFalse())
 		})
-
 	})
 })
diff --git a/stream.go b/stream.go
index a1c5feccf..03edae809 100644
--- a/stream.go
+++ b/stream.go
@@ -53,8 +53,10 @@ type streamI interface {
 	handleMaxStreamDataFrame(*wire.MaxStreamDataFrame)
 }
 
-var _ receiveStreamI = (streamI)(nil)
-var _ sendStreamI = (streamI)(nil)
+var (
+	_ receiveStreamI = (streamI)(nil)
+	_ sendStreamI    = (streamI)(nil)
+)
 
 // A Stream assembles the data from StreamFrames and provides a super-convenient Read-Interface
 //