client: Cancel context on IO errors

Also close the connection when the context expires.

client.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"crypto/tls"
 	"crypto/x509"
+	"io"
 	"net"
 	"net/url"
 	"time"
@@ -124,7 +125,22 @@ func (c *Client) Do(ctx context.Context, req *Request) (*Response, error) {
 
 	res := make(chan result, 1)
 	go func() {
-		resp, err := c.do(conn, req)
+		ctx, cancel := context.WithCancel(ctx)
+		done := ctx.Done()
+		cw := &contextWriter{
+			ctx:    ctx,
+			done:   done,
+			cancel: cancel,
+			wc:     conn,
+		}
+		cr := &contextReader{
+			ctx:    ctx,
+			done:   done,
+			cancel: cancel,
+			rc:     conn,
+		}
+
+		resp, err := c.do(cw, cr, req)
 		res <- result{resp, err}
 	}()
 
@@ -137,14 +153,14 @@ func (c *Client) Do(ctx context.Context, req *Request) (*Response, error) {
 	}
 }
 
-func (c *Client) do(conn net.Conn, req *Request) (*Response, error) {
+func (c *Client) do(w io.Writer, rc io.ReadCloser, req *Request) (*Response, error) {
 	// Write the request
-	if err := req.Write(conn); err != nil {
+	if err := req.Write(w); err != nil {
 		return nil, err
 	}
 
 	// Read the response
-	resp, err := ReadResponse(conn)
+	resp, err := ReadResponse(rc)
 	if err != nil {
 		return nil, err
 	}
@@ -206,3 +222,55 @@ func punycodeHostname(hostname string) (string, error) {
 	}
 	return idna.Lookup.ToASCII(hostname)
 }
+
+type contextReader struct {
+	ctx    context.Context
+	done   <-chan struct{}
+	cancel func()
+	rc     io.ReadCloser
+}
+
+func (r *contextReader) Read(p []byte) (int, error) {
+	select {
+	case <-r.done:
+		r.rc.Close()
+		return 0, r.ctx.Err()
+	default:
+	}
+	n, err := r.rc.Read(p)
+	if err != nil {
+		r.cancel()
+	}
+	return n, err
+}
+
+func (r *contextReader) Close() error {
+	r.cancel()
+	return r.rc.Close()
+}
+
+type contextWriter struct {
+	ctx    context.Context
+	done   <-chan struct{}
+	cancel func()
+	wc     io.WriteCloser
+}
+
+func (w *contextWriter) Write(b []byte) (int, error) {
+	select {
+	case <-w.done:
+		w.wc.Close()
+		return 0, w.ctx.Err()
+	default:
+	}
+	n, err := w.wc.Write(b)
+	if err != nil {
+		w.cancel()
+	}
+	return n, err
+}
+
+func (w *contextWriter) Close() error {
+	w.cancel()
+	return w.wc.Close()
+}