SourceGenerator.csproj改成netstandard2.0

Share/SourceGenerator/ET.SourceGenerator.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFramework>netstandard2.1</TargetFramework>
+        <TargetFramework>netstandard2.0</TargetFramework>
         <IncludeBuildOutput>false</IncludeBuildOutput>
         <Nullable>enable</Nullable>
         <LangVersion>12</LangVersion>