fix: explicitly enumerate protocols

Author: agoose77

lib/configproxy.js

@@ -397,14 +397,14 @@ export class ConfigurableProxy extends EventEmitter {
       proxyOptions.secure = false;
       proxyOptions.target.socketPath = decodeURIComponent(target.host);
       proxyOptions.target.pathname = (target.pathname ? target.pathname + "/" : "") + reqUrl;
+    } else if (target.protocol.startsWith("https")) {
+      proxyOptions.secure = true;
+      proxyOptions.agent = this.httpsAgent;
+    } else if (target.protocol.startsWith("http")) {
+      proxyOptions.secure = false;
+      proxyOptions.agent = this.httpAgent;
     } else {
-      proxyOptions.secure = target.protocol.slice(-2) === "s:";
-
-      if (proxyOptions.secure) {
-        proxyOptions.agent = this.httpsAgent;
-      } else {
-        proxyOptions.agent = this.httpAgent;
-      }
+      throw new Error(`Unexpected protocol ${target.protocol}`);
     }
 
     if (proxyOptions.secure && this.options.clientSsl) {