fix golint issue

Author: keegancsmith

cmd/src/main.go

@@ -267,7 +267,7 @@ func readConfig() (*config, error) {
 		// no SRC_PROXY; check for the standard proxy env variables HTTP_PROXY, HTTPS_PROXY, and NO_PROXY
 		if u, err := http.ProxyFromEnvironment(&http.Request{URL: cfg.EndpointURL}); err != nil {
 			// when there's an error, the value for the env variable is not a legit URL
-			return nil, fmt.Errorf("Invalid HTTP_PROXY or HTTPS_PROXY value: %w", err)
+			return nil, fmt.Errorf("invalid HTTP_PROXY or HTTPS_PROXY value: %w", err)
 		} else {
 			cfg.ProxyURL = u
 		}