# 检查通道中是否有可用数据

如果通道中没有数据，接收操作会被阻塞。

如果您不想阻塞怎么办？

您可能会想到，可以在执行接收操作之前检查通道中是否有数据。

您不能在Go语言中这样做，因为它可能不会正确工作。在您执行完检查操作后到执行接收操作之间的时间里，别的协程可能拿走数据。

如果您想避免无限的等待，您可以使用`select`添加[超时通道](/essential-go/22-channels-and-select/timeout-reading-from-a-channel-with-select.md)或[非阻塞等待](/essential-go/22-channels-and-select/non-blocking-receive-with-select.md)。


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