Only peek 1 byte

Make sure old clients that send bogus \r\n still work.
See: golang/go@bf5e19f

server.go

@@ -2056,7 +2056,7 @@ func (s *Server) serveConn(c net.Conn) (err error) {
 			// within the idle time.
 			if connRequestNum > 1 {
 				var b []byte
-				b, err = br.Peek(4)
+				b, err = br.Peek(1)
 				if len(b) == 0 {
 					// If reading from a keep-alive connection returns nothing it means
 					// the connection was closed (either timeout or from the other side).

server_test.go

@@ -23,6 +23,94 @@ import (
 // Make sure RequestCtx implements context.Context
 var _ context.Context = &RequestCtx{}
 
+func TestServerCRNLAfterPost_Pipeline(t *testing.T) {
+	t.Parallel()
+
+	s := &Server{
+		Handler: func(ctx *RequestCtx) {
+		},
+		Logger: &testLogger{},
+	}
+
+	ln := fasthttputil.NewInmemoryListener()
+	defer ln.Close()
+
+	go func() {
+		if err := s.Serve(ln); err != nil {
+			t.Errorf("unexpected error: %s", err)
+		}
+	}()
+
+	c, err := ln.Dial()
+	if err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
+	defer c.Close()
+	if _, err = c.Write([]byte("POST / HTTP/1.1\r\nHost: golang.org\r\nContent-Length: 3\r\n\r\nABC" +
+		"\r\n\r\n" + // <-- this stuff is bogus, but we'll ignore it
+		"GET / HTTP/1.1\r\nHost: golang.org\r\n\r\n")); err != nil {
+		t.Fatal(err)
+	}
+
+	br := bufio.NewReader(c)
+	var resp Response
+	if err := resp.Read(br); err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
+	if resp.StatusCode() != StatusOK {
+		t.Fatalf("unexpected status code: %d. Expecting %d", resp.StatusCode(), StatusOK)
+	}
+	if err := resp.Read(br); err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
+	if resp.StatusCode() != StatusOK {
+		t.Fatalf("unexpected status code: %d. Expecting %d", resp.StatusCode(), StatusOK)
+	}
+}
+
+func TestServerCRNLAfterPost(t *testing.T) {
+	t.Parallel()
+
+	s := &Server{
+		Handler: func(ctx *RequestCtx) {
+		},
+		Logger:      &testLogger{},
+		ReadTimeout: time.Millisecond * 1,
+	}
+
+	ln := fasthttputil.NewInmemoryListener()
+	defer ln.Close()
+
+	go func() {
+		if err := s.Serve(ln); err != nil {
+			t.Errorf("unexpected error: %s", err)
+		}
+	}()
+
+	c, err := ln.Dial()
+	if err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
+	defer c.Close()
+	if _, err = c.Write([]byte("POST / HTTP/1.1\r\nHost: golang.org\r\nContent-Length: 3\r\n\r\nABC" +
+		"\r\n\r\n", // <-- this stuff is bogus, but we'll ignore it
+	)); err != nil {
+		t.Fatal(err)
+	}
+
+	br := bufio.NewReader(c)
+	var resp Response
+	if err := resp.Read(br); err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
+	if resp.StatusCode() != StatusOK {
+		t.Fatalf("unexpected status code: %d. Expecting %d", resp.StatusCode(), StatusOK)
+	}
+	if err := resp.Read(br); err == nil {
+		t.Fatal("expected error") // We didn't send a request so we should get an error here.
+	}
+}
+
 func TestServerPipelineFlush(t *testing.T) {
 	t.Parallel()