Sql connection pool timeout

Question

Sql connection pool timeout

[Disclaimer]: I think I read every stackoverflow post about this already

I have long been racking my brains over this. I get the following exception in my asp.net web.api.

Exception thrown: 'System.InvalidOperationException' in mscorlib.dll
Additional Information: Timed out. The wait period expires before a connection is received from the pool. Perhaps this was due to the fact that all joined connections were used and the maximum pool size was reached.

Most people suggested that I look for leaked connections in my application. Here is my code. Now i'm sure i'm not leaking any connections

public async Task<IEnumerable<string>> Get()
    {
        var ds = new DataSet();
        var constring = "Data Source=xxx;Initial Catalog=xxx;User Id=xxx;Password=xxx;Max Pool Size=100";
        var asyncConnectionString = new SqlConnectionStringBuilder(constring)
        {
            AsynchronousProcessing = true
        }.ToString();


        using (var con = new SqlConnection(asyncConnectionString))
        using (var cmd = new SqlCommand("[dbo].[xxx]", con))
            {
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.AddWithValue("@x1", 1);
                cmd.Parameters.AddWithValue("@x2", "something");

                await con.OpenAsync();
                using (var rdr =await  cmd.ExecuteReaderAsync())
                {
                    if (rdr.HasRows)
                    {
                        ds.Load(rdr, LoadOption.OverwriteChanges, "MyTable");
                    }
                    rdr.Close();
                    con.Close();
                    ds.Dispose();
                }
            }
        //I know this looks wrong, just an empty api method to show the code
        return new string[] { "value1", "value2" };
    }