feat: add a --proxy parameter

cmd/dbc/main.go

@@ -154,6 +154,7 @@ type cmds struct {
 	Auth       *AuthCmd         `arg:"subcommand" help:"Manage driver registry credentials"`
 	Completion *completions.Cmd `arg:"subcommand,hidden"`
 	Quiet      bool             `arg:"-q,--quiet" help:"Suppress all output"`
+	Proxy      string           `arg:"--proxy" help:"Proxy server URL for HTTP requests"`
 }
 
 func (cmds) Version() string {
@@ -189,6 +190,13 @@ func main() {
 		}
 	}
 
+	if args.Proxy != "" {
+		if err := dbc.SetProxy(args.Proxy); err != nil {
+			fmt.Fprintf(os.Stderr, "Error setting proxy: %v\n", err)
+			os.Exit(1)
+		}
+	}
+
 	if p.Subcommand() == nil {
 		p.WriteHelp(os.Stdout)
 		os.Exit(1)

drivers.go

@@ -85,6 +85,34 @@ func (u *uaRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
 	return u.RoundTripper.RoundTrip(req)
 }
 
+// SetProxy configures the HTTP client to use the specified proxy server.
+// If proxy is empty, it uses the default transport (which may still respect HTTP_PROXY env var).
+func SetProxy(proxy string) error {
+	var transport http.RoundTripper = http.DefaultTransport
+	if proxy != "" {
+		proxyURL, err := url.Parse(proxy)
+		if err != nil {
+			return fmt.Errorf("invalid proxy URL: %w", err)
+		}
+		transport = &http.Transport{Proxy: http.ProxyURL(proxyURL)}
+	}
+
+	// Preserve the user agent from the current transport
+	var userAgent string
+	if ua, ok := DefaultClient.Transport.(*uaRoundTripper); ok {
+		userAgent = ua.userAgent
+	} else {
+		// Fallback, should not happen
+		userAgent = "dbc-cli"
+	}
+
+	DefaultClient.Transport = &uaRoundTripper{
+		RoundTripper: transport,
+		userAgent:    userAgent,
+	}
+	return nil
+}
+
 func init() {
 	info, ok := debug.ReadBuildInfo()
 	if ok {

drivers_test.go

@@ -0,0 +1,63 @@
+// Copyright 2026 Columnar Technologies Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package dbc
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSetProxy(t *testing.T) {
+	// Save original transport
+	originalTransport := DefaultClient.Transport
+
+	t.Cleanup(func() {
+		DefaultClient.Transport = originalTransport
+	})
+
+	t.Run("valid proxy URL", func(t *testing.T) {
+		err := SetProxy("http://proxy.example.com:8080")
+		require.NoError(t, err)
+
+		// Check that transport is set
+		ua, ok := DefaultClient.Transport.(*uaRoundTripper)
+		require.True(t, ok, "transport should be uaRoundTripper")
+
+		transport, ok := ua.RoundTripper.(*http.Transport)
+		require.True(t, ok, "inner transport should be http.Transport")
+
+		require.NotNil(t, transport.Proxy, "proxy should be set")
+	})
+
+	t.Run("empty proxy", func(t *testing.T) {
+		err := SetProxy("")
+		require.NoError(t, err)
+
+		ua, ok := DefaultClient.Transport.(*uaRoundTripper)
+		require.True(t, ok)
+
+		// Should use default transport
+		assert.Equal(t, http.DefaultTransport, ua.RoundTripper)
+	})
+
+	t.Run("invalid proxy URL", func(t *testing.T) {
+		err := SetProxy("://invalid")
+		assert.Error(t, err)
+		assert.Contains(t, err.Error(), "invalid proxy URL")
+	})
+}