fix build

Author: mythz

src/ServiceStack.Memory/NetCoreMemory.cs

@@ -189,6 +189,13 @@ public override ReadOnlyMemory<char> FromUtf8(ReadOnlySpan<byte> source)
         public override byte[] ToUtf8Bytes(ReadOnlySpan<char> source) => ToUtf8(source).ToArray();
 
         public override string FromUtf8Bytes(ReadOnlySpan<byte> source) => FromUtf8(source).ToString();
+
+        public override MemoryStream ToMemoryStream(ReadOnlySpan<byte> source)
+        {
+            var ms = MemoryStreamFactory.GetStream(source.Length);
+            ms.Write(source);
+            return ms;
+        }
     }    
 }
 

src/ServiceStack.Text/NetCoreMemory.cs

@@ -189,6 +189,7 @@ public override ReadOnlyMemory<char> FromUtf8(ReadOnlySpan<byte> source)
         public override byte[] ToUtf8Bytes(ReadOnlySpan<char> source) => ToUtf8(source).ToArray();
 
         public override string FromUtf8Bytes(ReadOnlySpan<byte> source) => FromUtf8(source).ToString();
+
         public override MemoryStream ToMemoryStream(ReadOnlySpan<byte> source)
         {
             var ms = MemoryStreamFactory.GetStream(source.Length);