Enable nullable annotations for Volo.Abp.DistributedLocking

framework/src/Volo.Abp.DistributedLocking/Volo.Abp.DistributedLocking.csproj

@@ -5,6 +5,8 @@
 
     <PropertyGroup>
         <TargetFrameworks>netstandard2.0;netstandard2.1;net7.0</TargetFrameworks>
+        <Nullable>enable</Nullable>
+        <WarningsAsErrors>Nullable</WarningsAsErrors>
         <AssemblyName>Volo.Abp.DistributedLocking</AssemblyName>
         <PackageId>Volo.Abp.DistributedLocking</PackageId>
         <AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wp8+wpa81;</AssetTargetFallback>

framework/src/Volo.Abp.DistributedLocking/Volo/Abp/DistributedLocking/MedallionAbpDistributedLock.cs

@@ -25,7 +25,7 @@ public class MedallionAbpDistributedLock : IAbpDistributedLock, ITransientDepend
         DistributedLockKeyNormalizer = distributedLockKeyNormalizer;
     }
 
-    public async Task<IAbpDistributedLockHandle> TryAcquireAsync(
+    public async Task<IAbpDistributedLockHandle?> TryAcquireAsync(
         string name,
         TimeSpan timeout = default,
         CancellationToken cancellationToken = default)