Update Actions to use specific framework

Signed-off-by: Aitor Perez Cedres <acedres@vmware.com>

Author: Zerpet

.github/workflows/main.yaml

@@ -44,7 +44,7 @@ jobs:
       - name: Restore
         run: dotnet restore --verbosity=normal
       - name: ApiGen
-        run: dotnet run --project ./projects/Apigen/Apigen.csproj --apiName:AMQP_0_9_1 ./projects/specs/amqp0-9-1.stripped.xml ./gensrc/autogenerated-api-0-9-1.cs
+        run: dotnet run --framework "netcoreapp3.1" --project ./projects/Apigen/Apigen.csproj --apiName:AMQP_0_9_1 ./projects/specs/amqp0-9-1.stripped.xml ./gensrc/autogenerated-api-0-9-1.cs
       - name: Build
         run: dotnet build --no-restore --verbosity=normal
       - name: Test
@@ -70,7 +70,9 @@ jobs:
       - name: Setup .NET
         uses: actions/setup-dotnet@v2
         with:
-          dotnet-version: 3.1.x
+          dotnet-version: |
+            3.1.x
+            6.0.x
       - name: Cache NuGet packages
         uses: actions/cache@v3
         with:
@@ -83,7 +85,7 @@ jobs:
       - name: Restore
         run: dotnet restore --verbosity=normal
       - name: ApiGen
-        run: dotnet run --project ./projects/Apigen/Apigen.csproj --apiName:AMQP_0_9_1 ./projects/specs/amqp0-9-1.stripped.xml ./gensrc/autogenerated-api-0-9-1.cs
+        run: dotnet run --framework "netcoreapp3.1" --project ./projects/Apigen/Apigen.csproj --apiName:AMQP_0_9_1 ./projects/specs/amqp0-9-1.stripped.xml ./gensrc/autogenerated-api-0-9-1.cs
       - name: Build
         run: dotnet build --no-restore --verbosity=normal
       - name: Test