HttpBaseReadAsync 方法
            异步读取HTTP块段的内容。
            
命名空间: TouchSocket.Http程序集: TouchSocket.Http (在 TouchSocket.Http.dll 中) 版本:4.0.0-beta.143+5fcca7a4e70968794985dc3793adc50531308be6
public abstract ValueTask<HttpReadOnlyMemoryBlockResult> ReadAsync(
	CancellationToken cancellationToken = default
)
Public MustOverride Function ReadAsync ( 
	Optional cancellationToken As CancellationToken = Nothing
) As ValueTask(Of HttpReadOnlyMemoryBlockResult)
abstract ReadAsync : 
        ?cancellationToken : CancellationToken 
(* Defaults:
        let _cancellationToken = defaultArg cancellationToken new CancellationToken()
*)
-> ValueTask<HttpReadOnlyMemoryBlockResult> 
- cancellationToken  CancellationToken  (Optional)
 - 用于取消异步操作的令牌。
 
ValueTaskHttpReadOnlyMemoryBlockResult返回一个
IReadOnlyMemoryBlockResult,表示异步读取操作的结果。