fixed sql syntax error.

src/DotNetCore.CAP.PostgreSql/PostgreSqlStorageConnection.cs

@@ -37,10 +37,7 @@ namespace DotNetCore.CAP.PostgreSql
 
         public Task<IFetchedMessage> FetchNextMessageAsync()
         {
-            var sql = $@"
-SELECT ""MessageId"",""MessageType"" FROM ""{_options.Schema}"".""queue"" LIMIT 1 FOR UPDATE;
-DELETE FROM ""{_options.Schema}"".""queue"" LIMIT 1;";
-            
+            var sql = $@"DELETE FROM ""{_options.Schema}"".""queue"" WHERE ""MessageId"" = (SELECT ""MessageId"" FROM ""{_options.Schema}"".""queue"" LIMIT 1) RETURNING *;";
             return FetchNextMessageCoreAsync(sql);
         }
 

src/DotNetCore.CAP.PostgreSql/PostgreSqlStorageTransaction.cs

@@ -28,7 +28,7 @@ namespace DotNetCore.CAP.PostgreSql
         {
             if (message == null) throw new ArgumentNullException(nameof(message));
 
-            var sql = $"UPDATE [{_schema}].[Published] SET [Retries] = @Retries,[ExpiresAt] = @ExpiresAt,[StatusName]=@StatusName WHERE Id=@Id;";
+            var sql = $@"UPDATE ""{_schema}"".""published"" SET ""Retries""=@Retries,""ExpiresAt""=@ExpiresAt,""StatusName""=@StatusName WHERE ""Id""=@Id;";
             _dbConnection.Execute(sql, message, _dbTransaction);
         }
 
@@ -36,7 +36,7 @@ namespace DotNetCore.CAP.PostgreSql
         {
             if (message == null) throw new ArgumentNullException(nameof(message));
 
-            var sql = $"UPDATE [{_schema}].[Received] SET [Retries] = @Retries,[ExpiresAt] = @ExpiresAt,[StatusName]=@StatusName WHERE Id=@Id;";
+            var sql = $@"UPDATE ""{_schema}"".""received"" SET ""Retries""=@Retries,""ExpiresAt""=@ExpiresAt,""StatusName""=@StatusName WHERE ""Id""=@Id;";
             _dbConnection.Execute(sql, message, _dbTransaction);
         }
 
@@ -44,7 +44,7 @@ namespace DotNetCore.CAP.PostgreSql
         {
             if (message == null) throw new ArgumentNullException(nameof(message));
 
-            var sql = $"INSERT INTO [{_schema}].[Queue] values(@MessageId,@MessageType);";
+            var sql = $@"INSERT INTO ""{_schema}"".""queue"" values(@MessageId,@MessageType);";
             _dbConnection.Execute(sql, new CapQueue { MessageId = message.Id, MessageType = MessageType.Publish }, _dbTransaction);
         }
 
@@ -52,7 +52,7 @@ namespace DotNetCore.CAP.PostgreSql
         {
             if (message == null) throw new ArgumentNullException(nameof(message));
 
-            var sql = $"INSERT INTO [{_schema}].[Queue] values(@MessageId,@MessageType);";
+            var sql = $@"INSERT INTO ""{_schema}"".""queue"" values(@MessageId,@MessageType);";
             _dbConnection.Execute(sql, new CapQueue { MessageId = message.Id, MessageType = MessageType.Subscribe }, _dbTransaction);
         }