Fix lint await_only_futures (#104)

diff --git a/lib/src/client_credentials_grant.dart b/lib/src/client_credentials_grant.dart
index ab13a3f..1d79c80 100644
--- a/lib/src/client_credentials_grant.dart
+++ b/lib/src/client_credentials_grant.dart
@@ -71,7 +71,7 @@
   var response = await httpClient.post(authorizationEndpoint,
       headers: headers, body: body);
 
-  var credentials = await handleAccessTokenResponse(response,
+  var credentials = handleAccessTokenResponse(response,
       authorizationEndpoint, startTime, scopes?.toList() ?? [], delimiter,
       getParameters: getParameters);
   return Client(credentials,
diff --git a/lib/src/credentials.dart b/lib/src/credentials.dart
index 88a8f45..2acc8f2 100644
--- a/lib/src/credentials.dart
+++ b/lib/src/credentials.dart
@@ -241,7 +241,7 @@
 
     var response =
         await httpClient.post(tokenEndpoint, headers: headers, body: body);
-    var credentials = await handleAccessTokenResponse(
+    var credentials = handleAccessTokenResponse(
         response, tokenEndpoint, startTime, scopes, _delimiter,
         getParameters: _getParameters);
 
diff --git a/lib/src/resource_owner_password_grant.dart b/lib/src/resource_owner_password_grant.dart
index f54ac85..b1cc772 100644
--- a/lib/src/resource_owner_password_grant.dart
+++ b/lib/src/resource_owner_password_grant.dart
@@ -83,7 +83,7 @@
   var response = await httpClient.post(authorizationEndpoint,
       headers: headers, body: body);
 
-  var credentials = await handleAccessTokenResponse(
+  var credentials = handleAccessTokenResponse(
       response, authorizationEndpoint, startTime, scopes?.toList(), delimiter,
       getParameters: getParameters);
   return Client(credentials,