GitHub Action CI: Add Go source file format check (#6090)

https://github.com/XTLS/Xray-core/pull/6057#issuecomment-4364819830

And https://github.com/XTLS/Xray-core/pull/6149#issuecomment-4546876261

common/buf/multi_buffer.go

@@ -38,8 +38,8 @@ func MergeMulti(dest MultiBuffer, src MultiBuffer) (MultiBuffer, MultiBuffer) {
 // MergeBytes merges the given bytes into MultiBuffer and return the new address of the merged MultiBuffer.
 func MergeBytes(dest MultiBuffer, src []byte) MultiBuffer {
 	n := len(dest)
-	if n > 0 && !(dest)[n-1].IsFull() {
-		nBytes, _ := (dest)[n-1].Write(src)
+	if n > 0 && !dest[n-1].IsFull() {
+		nBytes, _ := dest[n-1].Write(src)
 		src = src[nBytes:]
 	}