feat: add typing define.

index.d.ts

@@ -0,0 +1,43 @@
+declare module "agentkeepalive" {
+  import * as http from 'http';
+  import * as https from 'https';
+
+  interface AgentStatus {
+    createSocketCount: number,
+    createSocketErrorCount: number,
+    closeSocketCount: number,
+    errorSocketCount: number,
+    timeoutSocketCount: number,
+    requestCount: number,
+    freeSockets: object,
+    sockets: object,
+    requests: object,
+  }
+
+  interface HttpOptions extends http.AgentOptions {
+    freeSocketKeepAliveTimeout?: number;
+    timeout?: number;
+    socketActiveTTL?: number;
+  }
+
+  interface HttpsOptions extends https.AgentOptions {
+    freeSocketKeepAliveTimeout?: number;
+    timeout?: number;
+    socketActiveTTL?: number;
+  }
+
+  class internal extends http.Agent {
+    constructor(opts?: HttpOptions);
+    readonly statusChanged: boolean;
+    createSocket(req: http.IncomingMessage, options: http.RequestOptions, cb: Function): void;
+    getCurrentStatus(): AgentStatus;
+  }
+
+  namespace internal {
+    export class HttpsAgent extends internal {
+      constructor(opts?: HttpsOptions);
+    }
+  }
+
+  export = internal;
+}