Treat all errors on first header byte read as EOF. This eliminates numerous and useless 'connection reset by peer' log messages for keep-alive connections on busy server

header.go

@@ -555,11 +555,9 @@ func (h *ResponseHeader) tryRead(r *bufio.Reader, n int) error {
 	h.Clear()
 	b, err := r.Peek(n)
 	if len(b) == 0 {
-		if err == io.EOF {
-			return err
-		}
-		if err == nil {
-			panic("bufio.Reader.Peek() returned nil, nil")
+		// treat all errors on the first byte read as EOF
+		if n == 1 || err == io.EOF {
+			return io.EOF
 		}
 		return fmt.Errorf("error when reading response headers: %s", err)
 	}
@@ -597,11 +595,9 @@ func (h *RequestHeader) tryRead(r *bufio.Reader, n int) error {
 	h.Clear()
 	b, err := r.Peek(n)
 	if len(b) == 0 {
-		if err == io.EOF {
-			return err
-		}
-		if err == nil {
-			panic("bufio.Reader.Peek() returned nil, nil")
+		// treat all errors on the first byte read as EOF
+		if n == 1 || err == io.EOF {
+			return io.EOF
 		}
 		return fmt.Errorf("error when reading request headers: %s", err)
 	}

header_test.go

@@ -10,6 +10,42 @@ import (
 	"testing"
 )
 
+func TestResponseHeaderFirstByteReadEOF(t *testing.T) {
+	var h ResponseHeader
+
+	r := &errorReader{fmt.Errorf("non-eof error")}
+	br := bufio.NewReader(r)
+	err := h.Read(br)
+	if err == nil {
+		t.Fatalf("expecting error")
+	}
+	if err != io.EOF {
+		t.Fatalf("unexpected error %s. Expecting %s", err, io.EOF)
+	}
+}
+
+func TestRequestHeaderFirstByteReadEOF(t *testing.T) {
+	var h RequestHeader
+
+	r := &errorReader{fmt.Errorf("non-eof error")}
+	br := bufio.NewReader(r)
+	err := h.Read(br)
+	if err == nil {
+		t.Fatalf("expecting error")
+	}
+	if err != io.EOF {
+		t.Fatalf("unexpected error %s. Expecting %s", err, io.EOF)
+	}
+}
+
+type errorReader struct {
+	err error
+}
+
+func (r *errorReader) Read(p []byte) (int, error) {
+	return 0, r.err
+}
+
 func TestRequestHeaderEmptyMethod(t *testing.T) {
 	var h RequestHeader