有没有办法让频道只接收？

这显然有效:

// cast chan string to <-chan string
func RecOnly(c chan string) <-chan string {
    return c
}

func main() {
    a := make(chan string, 123)
    b := RecOnly(a)

    a <- "one"
    a <- "two"
    //b <- "beta" // compile error because of send to receive-only channel
    fmt.Println("a", <-a, "b", <-b)
}

但是,如果没有声明新功能,是否有一个单行代码？

您可以将b类型明确定义为仅接收通道,并将其值设置为a.您也可以转发a到仅接收频道.来自Go规范:

频道可能仅限于发送或仅通过转换或分配来接收.

func main() {
    a := make(chan string, 123)
    var b <-chan string = a // or, b := (<-chan string)(a)

    a <- "one"
    a <- "two"
    //b <- "beta" // compile error because of send to receive-only channel
    fmt.Println("a", <-a, "b", <-b)
}