feat: Add support for agent option. [#78] (#81)

* feat: Add support for `agent` option. [#78]

* fix: Fix README.md.

README.md

@@ -15,20 +15,25 @@ npm install get-jwks
 ### Options
 
 ```js
+const https = require('https')
 const buildGetJwks = require('get-jwks')
 
 const getJwks = buildGetJwks({
   max: 100,
   maxAge: 60 * 1000,
   allowedDomains: ['https://example.com'],
   providerDiscovery: false,
+  agent: new https.Agent({
+    keepAlive: true,
+  }),
 })
 ```
 
 - `max`: Max items to hold in cache. Defaults to 100.
 - `maxAge`: Milliseconds an item will remain in cache. Defaults to 60s.
 - `allowedDomains`: Array of allowed domains. By default all domains are allowed.
-- `providerDiscovery`: Indicates if the Provider Configuration Information is used to automatically get the jwks_uri from the [OpenID Provider Discovery Endpoint](https://openid.net/specs/openid-connect-discovery-1_0.html#ProviderConfig). This endpoint is exposing the [Provider Metadata](https://openid.net/specs/openid-connect-discovery-1_0.html#ProviderMetadata). With this flag set to true the domain will be treated as the OpenID Issuer which is the iss property in the token. Defaults to false
+- `providerDiscovery`: Indicates if the Provider Configuration Information is used to automatically get the jwks_uri from the [OpenID Provider Discovery Endpoint](https://openid.net/specs/openid-connect-discovery-1_0.html#ProviderConfig). This endpoint is exposing the [Provider Metadata](https://openid.net/specs/openid-connect-discovery-1_0.html#ProviderMetadata). With this flag set to true the domain will be treated as the OpenID Issuer which is the iss property in the token. Defaults to false.
+- `agent`: The custom agent to use for requests, as specified in [node-fetch documentation](https://github.com/node-fetch/node-fetch#custom-agent). Defaults to `null`.
 
 > `max` and `maxAge` are provided to [lru-cache](https://www.npmjs.com/package/lru-cache).
 

package.json

@@ -7,7 +7,7 @@
     "node": ">=10"
   },
   "scripts": {
-    "test": "tap",
+    "test": "tap test/*.spec.js",
     "lint": "eslint ."
   },
   "repository": {

src/get-jwks.js

@@ -15,42 +15,44 @@ function ensureTrailingSlash(domain) {
   return domain.endsWith('/') ? domain : `${domain}/`
 }
 
-async function getJwksUri(normalizedDomain) {
-  const response = await fetch(
-    `${normalizedDomain}.well-known/openid-configuration`,
-    {
-      timeout: 5000,
-    }
-  )
-  const body = await response.json()
-
-  if (!response.ok) {
-    const error = new Error(response.statusText)
-    error.response = response
-    error.body = body
-    throw error
-  }
-
-  if (!body.jwks_uri) {
-    throw new Error(errors.NO_JWKS_URI)
-  }
-
-  return body.jwks_uri
-}
-
 function buildGetJwks(options = {}) {
   const max = options.max || 100
   const maxAge = options.maxAge || 60 * 1000 /* 1 minute */
   const allowedDomains = (options.allowedDomains || []).map(ensureTrailingSlash)
   const providerDiscovery = options.providerDiscovery || false
-
+  const agent = options.agent || null
+
   const staleCache = new LRU({ max: max * 2, maxAge })
   const cache = new LRU({
     max,
     maxAge,
     dispose: staleCache.set.bind(staleCache),
   })
 
+  async function getJwksUri(normalizedDomain) {
+    const response = await fetch(
+      `${normalizedDomain}.well-known/openid-configuration`,
+      {
+        agent,
+        timeout: 5000,        
+      }
+    )
+    const body = await response.json()
+
+    if (!response.ok) {
+      const error = new Error(response.statusText)
+      error.response = response
+      error.body = body
+      throw error
+    }
+
+    if (!body.jwks_uri) {
+      throw new Error(errors.NO_JWKS_URI)
+    }
+
+    return body.jwks_uri
+  }
+
   async function getPublicKey(signature) {
     return jwkToPem(await this.getJwk(signature))
   }
@@ -95,7 +97,7 @@ function buildGetJwks(options = {}) {
       ? await getJwksUri(normalizedDomain)
       : `${normalizedDomain}.well-known/jwks.json`
 
-    const response = await fetch(jwksUri, { timeout: 5000 })
+    const response = await fetch(jwksUri, { agent, timeout: 5000 })
     const body = await response.json()
 
     if (!response.ok) {