Azure functions can not support send a http request with Authorization header

` HttpClient client = new HttpClient();
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", "**********");
var response =
client.GetAsync("***************").Result.Content.ReadAsStringAsync().Result;
`

these code run very well in local with azure-functions-core-tools, but not well in the production environment that in azure . Can you help me to solve this case. thanks very much.

this is my execution id :Function completed (Failure, Id=b0ddfab2-e451-4eb1-a7c4-9462a7cf879b, Duration=12392ms)