Request for the use of SocketsHttpHandler

[Satish Viswanathan]

@tmenier I have started using the version 4.0.0-pre4 and was able to make Http/2 calls. Thank you for this feature addition. if we can have SocketsHttpHandler as the default handler then we can set the properties like EnableMultipleHttp2Connections , connection pooling, Gzip compression etc.

On Http/2 I was able to get it working by setting the global property FlurlHttp.GlobalSettings.HttpVersion = "2.0". It would be great if we can set this per HttpClient also other properties like DefaultVersionPolicy. Currently we can set it at the client level but I ran into the following issue.

 var httpClient = _flurlClientFactory.Get(serviceOptions.Url);
 httpClient.BaseUrl = serviceOptions.Url;
httpClient.HttpClient.DefaultRequestVersion = new Version(2, 0);
httpClient.HttpClient.DefaultVersionPolicy = HttpVersionPolicy.RequestVersionOrLower;

With the above code if I had a client created once with those properties set then next time when I try to get the same client using the flurl factory and set these properties then we would get the following error.

"System.InvalidOperationException : This instance has already started one or more requests. Properties can only be modified before sending the first request."

[Todd Menier]

In 4.0, SocketsHttpHandler will be used by Flurl on supported platforms and will be easily configurable via IFlurlClientBuilder.ConfigureInnerHandler. See #770 for details.

[Satish Viswanathan]

Thank you @tmenier

[Todd Menier]

Heads up: This implementation is changing in prerelease 6 to address #772. Here's the new way:

• Don't call ConfigureInnerHandler - it will be for configuring an HttpClientHandler on all platforms.
• Call UseSocketsHttpHandler instead - it will be for configuring a SocketsHttpHandler instead and is only available on supported platforms.

Attempting to call both will throw an exception, so definitely avoid that.