Update lib/fluent/plugin/out_s3.rb

Sure, lets try this.

Co-authored-by: Yuta Iwama <[email protected]>
Signed-off-by: riquemon <[email protected]>

Author: riquemon

lib/fluent/plugin/out_s3.rb

@@ -486,7 +486,11 @@ def setup_credentials
         elsif c.sts_endpoint_url
           credentials_options[:client] = Aws::STS::Client.new(endpoint: c.sts_endpoint_url)
         elsif @region
-          credentials_options[:client] = Aws::STS::Client.new(region: @region)
+opt = @s3_region ? { region: @s3_region } : {}
+opt[:http_proxy] = c.sts_http_proxy if c.sts_http_proxy
+opt[:endpoint_url] = c.sts_endpoint_url if c.sts_endpoint_url
+
+credentials_options[:client] = Aws::STS::Client.new(**opt)     
         end
         options[:credentials] = Aws::AssumeRoleCredentials.new(credentials_options)
       when @web_identity_credentials