Target and test .NET 7 instead of 6

Where a concrete framework is required, target the most recent, which is
now .NET 7.

Signed-off-by: Kevin Locke <kevin@kevinlocke.name>

.github/workflows/dotnet.yml

@@ -37,8 +37,8 @@ jobs:
         # https://github.com/actions/setup-dotnet/issues/93
         # Poses problems for versions incompatible with worker image:
         # https://github.com/actions/setup-dotnet/issues/23#issuecomment-523554330
-        # Note: Must quote value.  6.0 becomes 6, which silently fails.
-        - '6.0'
+        # Note: Must quote value.  7.0 becomes 7, which silently fails.
+        - '7.0'
         # Uncomment to build using an earlier SDK version:
         # - 3.1
     env:

NetCoreProject.UnitTests/NetCoreProject.UnitTests.csproj

@@ -4,7 +4,7 @@
     <Description>Unit tests for NetCoreProject.</Description>
 
     <!-- Multi-target all frameworks to test, newest first (for VS runner) -->
-    <TargetFrameworks>net6.0</TargetFrameworks>
+    <TargetFrameworks>net7.0</TargetFrameworks>
     <!-- Test older frameworks in CI (to avoid requiring devs to install) -->
     <!--
       TODO: Test opportunistically outside of CI?

NetCoreProject/NetCoreProject.csproj

@@ -17,7 +17,7 @@
 
   <PropertyGroup Condition="'$(OutputType)'=='Exe'">
     <!-- Need a "concrete" framework (i.e. not netstandard) for Exe -->
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net7.0</TargetFramework>
 
     <!-- Configure class with Main method entry point -->
     <StartupObject>NetCoreProject.Program</StartupObject>