为什么go要求您在变量名前添加＆？

Here is a snippet that I am looking at:

var t txn
t.c = c
err := c.read(&t.req)

Why do you have to write &t and not just t.req?

You don't always have to use the ampersand. In your example it depends on the signature of c.read, which asks for a pointer (* before the type, such as *MyStruct). & returns the address of a value, giving you a pointer to it, so &t.req satisfies read's signature.

For further reading, see the FAQ on pointers and the spec on Address operators.