Add OTLP/HTTP binary protobuf trace exporter for .NET open-telemetry#…

…2292 (open-telemetry#2292)

- added NET 5.0 to list of target frameworks
- adapted HttpHandler.Send method implementation according to used target

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/HttpHandler.cs

@@ -47,9 +47,11 @@ public void Dispose()
 
         public HttpResponseMessage Send(HttpRequestMessage request, CancellationToken cancellationToken)
         {
-            // TODO: replace by synchronous vesrion of Send method when it becomes availabe.
-            // See https://github.com/dotnet/runtime/pull/34948 (should be available starting form .NET 5.0).
+#if NET5_0
+            return this.HttpClient.Send(request);
+#else
             return AsyncHelper.RunSync(() => this.HttpClient.SendAsync(request));
+#endif
         }
     }
 }

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/OpenTelemetry.Exporter.OpenTelemetryProtocol.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;netstandard2.1;net461</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;netstandard2.1;net461;net5.0</TargetFrameworks>
     <Description>OpenTelemetry protocol exporter for OpenTelemetry .NET</Description>
     <PackageTags>$(PackageTags);OTLP</PackageTags>
     <MinVerTagPrefix>core-</MinVerTagPrefix>

test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpHttpTraceExporterTests.cs

@@ -47,7 +47,7 @@ static OtlpHttpTraceExporterTests()
         }
 
         [Fact]
-        public void OtlpExporter_BadArgs()
+        public void AddOtlpHttpExporter_BadArgs_Throws()
         {
             TracerProviderBuilder builder = null;
             Assert.Throws<ArgumentNullException>(() => builder.AddOtlpHttpExporter());