use new function to read proxy settings from environment, preferring SRC_PROXY if present

Author: peterguy

internal/api/api.go

@@ -99,9 +99,17 @@ func buildTransport(opts ClientOpts, flags *Flags) *http.Transport {
 	}
 
 	if opts.ProxyURL != nil || opts.ProxyPath != "" {
+		// Explicit SRC_PROXY configuration takes precedence.
 		transport = withProxyTransport(transport, opts.ProxyURL, opts.ProxyPath)
+	} else if proxyURL := envProxyURL(opts.Endpoint); proxyURL != nil && proxyURL.Scheme == "https" {
+		// For HTTPS proxies discovered via standard env vars, use our custom
+		// dialer to force HTTP/1.1 for the CONNECT tunnel. Many proxy servers
+		// don't support HTTP/2 CONNECT, which Go may negotiate via ALPN when
+		// TLS-connecting to an https:// proxy.
+		transport = withProxyTransport(transport, proxyURL, "")
 	}
-
+	// For http:// and socks5:// proxies from standard env vars, the cloned
+	// transport's default Proxy handles them correctly without intervention.
 	return transport
 }