add cmdexec package to execute commands on remote hosts via SSH

internal/cmdexec/remote.go

@@ -0,0 +1,59 @@
+package cmdexec
+
+import (
+	"context"
+	"fmt"
+	"golang.org/x/crypto/ssh"
+	"strings"
+)
+
+type Remote struct {
+	client *ssh.Client
+}
+
+// Run runs the command on the remote host and returns its output with all leading and trailing
+// white space removed.
+func (r *Remote) Run(ctx context.Context, cmd string) (string, error) {
+	session, err := r.client.NewSession()
+	if err != nil {
+		return "", fmt.Errorf("create session: %w", err)
+	}
+	defer func() {
+		_ = session.Close()
+	}()
+
+	// Run the command in a goroutine to be able to cancel it.
+	type result struct {
+		out string
+		err error
+	}
+	done := make(chan result)
+	go func() {
+		outBytes, outErr := session.CombinedOutput(cmd)
+		res := result{
+			err: outErr,
+		}
+		if outErr == nil {
+			res.out = strings.TrimSpace(string(outBytes))
+		}
+		done <- res
+	}()
+
+	select {
+	case res := <-done:
+		if res.err != nil {
+			return "", fmt.Errorf("run command on remote host: %w", res.err)
+		}
+		return res.out, nil
+	case <-ctx.Done():
+		if err = session.Signal(ssh.SIGINT); err != nil {
+			return "", fmt.Errorf("send interrupt signal to remote process: %w", err)
+		}
+		return "", fmt.Errorf("canceled: %w", ctx.Err())
+	}
+}
+
+// Close closes the connection to the remote host.
+func (r *Remote) Close() error {
+	return r.client.Close()
+}