ssh: add func DialContext

DialContext starts a client connection to the given SSH server using the supplied Context.
The supplied Context affects the dial and handshake. If it expires after the connection
is opened, it has no effect on the resulting Client.

Author: ydnar

ssh/client.go

@@ -6,6 +6,7 @@ package ssh
 
 import (
 	"bytes"
+	"context"
 	"errors"
 	"fmt"
 	"net"
@@ -168,6 +169,50 @@ func (c *Client) handleChannelOpens(in <-chan NewChannel) {
 	c.mu.Unlock()
 }
 
+// DialContext starts a client connection to the given SSH server. It is a
+// convenience function that connects to the given network address,
+// initiates the SSH handshake, and then sets up a Client.
+//
+// The provided Context must be non-nil. If the context expires before the
+// connection is complete, an error is returned. Once successfully connected,
+// any expiration of the context will not affect the connection.
+//
+// See [Dial] for additional information.
+func DialContext(ctx context.Context, network, addr string, config *ClientConfig) (*Client, error) {
+	d := net.Dialer{
+		Timeout: config.Timeout,
+	}
+	conn, err := d.DialContext(ctx, network, addr)
+	if err != nil {
+		return nil, err
+	}
+	type result struct {
+		client *Client
+		err    error
+	}
+	ch := make(chan result)
+	go func() {
+		var client *Client
+		c, chans, reqs, err := NewClientConn(conn, addr, config)
+		if err == nil {
+			client = NewClient(c, chans, reqs)
+		}
+		select {
+		case ch <- result{client, err}:
+		case <-ctx.Done():
+			if client != nil {
+				client.Close()
+			}
+		}
+	}()
+	select {
+	case res := <-ch:
+		return res.client, res.err
+	case <-ctx.Done():
+		return nil, context.Cause(ctx)
+	}
+}
+
 // Dial starts a client connection to the given SSH server. It is a
 // convenience function that connects to the given network address,
 // initiates the SSH handshake, and then sets up a Client.  For access