diff --git a/format.go b/format.go
index 8f2a2e2..5062a41 100644
--- a/format.go
+++ b/format.go
@@ -1,7 +1,7 @@
 package shadowsocks
 
 //go:generate go install -v mvdan.cc/gofumpt@latest
-//go:generate go install -v github.com/daixiang0/gci@latest
+//go:generate go install -v github.com/daixiang0/gci@v0.4.0
 //go:generate gofumpt -l -w .
 //go:generate gofmt -s -w .
-//go:generate gci write .
+//go:generate gci write -s "standard,prefix(github.com/sagernet/),default" .
diff --git a/shadowaead/aead.go b/shadowaead/aead.go
index 3ecaab4..e29789f 100644
--- a/shadowaead/aead.go
+++ b/shadowaead/aead.go
@@ -379,18 +379,18 @@ type BufferedWriter struct {
 }
 
 func (w *BufferedWriter) Write(p []byte) (n int, err error) {
-	var index int
 	for {
-		cachedN := copy(w.data[w.reversed+w.index:], p[index:])
-		if cachedN == len(p[index:]) {
-			w.index += cachedN
-			return cachedN, nil
+		cachedN := copy(w.data[w.reversed+w.index:], p[n:])
+		w.index += cachedN
+		if cachedN == len(p[n:]) {
+			n += cachedN
+			return
 		}
 		err = w.Flush()
 		if err != nil {
 			return
 		}
-		index += cachedN
+		n += cachedN
 	}
 }
 
@@ -412,6 +412,7 @@ func (w *BufferedWriter) Flush() error {
 	increaseNonce(w.upstream.nonce)
 	_, err := w.upstream.upstream.Write(w.upstream.buffer[:w.reversed+offset+len(packet)])
 	w.reversed = 0
+	w.index = 0
 	return err
 }
 
diff --git a/shadowaead/protocol.go b/shadowaead/protocol.go
index ae487ef..3ebb309 100644
--- a/shadowaead/protocol.go
+++ b/shadowaead/protocol.go
@@ -14,6 +14,7 @@ import (
 	M "github.com/sagernet/sing/common/metadata"
 	N "github.com/sagernet/sing/common/network"
 	"github.com/sagernet/sing/common/rw"
+
 	"golang.org/x/crypto/chacha20poly1305"
 	"golang.org/x/crypto/hkdf"
 )
diff --git a/shadowaead/service.go b/shadowaead/service.go
index a905f53..af58c84 100644
--- a/shadowaead/service.go
+++ b/shadowaead/service.go
@@ -19,6 +19,7 @@ import (
 	N "github.com/sagernet/sing/common/network"
 	"github.com/sagernet/sing/common/rw"
 	"github.com/sagernet/sing/common/udpnat"
+
 	"golang.org/x/crypto/chacha20poly1305"
 )
 
diff --git a/shadowaead_2022/protocol.go b/shadowaead_2022/protocol.go
index c7011e2..4cafb9b 100644
--- a/shadowaead_2022/protocol.go
+++ b/shadowaead_2022/protocol.go
@@ -8,7 +8,6 @@ import (
 	"crypto/sha256"
 	"encoding/base64"
 	"encoding/binary"
-	"github.com/sagernet/sing/common/random"
 	"io"
 	"math"
 	mRand "math/rand"
@@ -26,7 +25,9 @@ import (
 	E "github.com/sagernet/sing/common/exceptions"
 	M "github.com/sagernet/sing/common/metadata"
 	N "github.com/sagernet/sing/common/network"
+	"github.com/sagernet/sing/common/random"
 	"github.com/sagernet/sing/common/rw"
+
 	"golang.org/x/crypto/chacha20poly1305"
 	"lukechampine.com/blake3"
 )
diff --git a/shadowaead_2022/relay.go b/shadowaead_2022/relay.go
index 71bb26b..cfdf3fd 100644
--- a/shadowaead_2022/relay.go
+++ b/shadowaead_2022/relay.go
@@ -18,6 +18,7 @@ import (
 	M "github.com/sagernet/sing/common/metadata"
 	N "github.com/sagernet/sing/common/network"
 	"github.com/sagernet/sing/common/udpnat"
+
 	"lukechampine.com/blake3"
 )
 
diff --git a/shadowaead_2022/service.go b/shadowaead_2022/service.go
index b23316e..582c0e7 100644
--- a/shadowaead_2022/service.go
+++ b/shadowaead_2022/service.go
@@ -27,6 +27,7 @@ import (
 	N "github.com/sagernet/sing/common/network"
 	"github.com/sagernet/sing/common/replay"
 	"github.com/sagernet/sing/common/udpnat"
+
 	"golang.org/x/crypto/chacha20poly1305"
 )
 
diff --git a/shadowaead_2022/service_multi.go b/shadowaead_2022/service_multi.go
index 241313d..980e400 100644
--- a/shadowaead_2022/service_multi.go
+++ b/shadowaead_2022/service_multi.go
@@ -20,6 +20,7 @@ import (
 	M "github.com/sagernet/sing/common/metadata"
 	N "github.com/sagernet/sing/common/network"
 	"github.com/sagernet/sing/common/rw"
+
 	"lukechampine.com/blake3"
 )
 
diff --git a/shadowstream/protocol.go b/shadowstream/protocol.go
index 567b785..0af89c4 100644
--- a/shadowstream/protocol.go
+++ b/shadowstream/protocol.go
@@ -15,6 +15,7 @@ import (
 	"github.com/sagernet/sing/common/buf"
 	M "github.com/sagernet/sing/common/metadata"
 	N "github.com/sagernet/sing/common/network"
+
 	"golang.org/x/crypto/chacha20"
 )