阻止go build覆盖go.mod中的版本

Question

I have a go module that imports project foo. foo's latest tag says v1.4

when i do a go build in my project, it updates go.mod to say

module github.com/myid/mymod

require (
   github.com/myid/foo v1.4
)

I want it to use the master branch instead of v1.4 tag...so i did a go get github.com/myid/foo@master and it downloaded the master branch in pkg and updated go.mod to say

require (
    github.com/myid/foo v1-XXXXXXX-XXXXXXX
)

I verify that the hash is the same as master

but when i do go build again, it gets updated back to the latest tag.

how do i get it to use the master branch and not switch back to v1.4?

Thanks