如何转换具有相同签名的函数类型?

In a package, I have this:

package pkg1

type SomeFuncType func (a interface{}, b interface{}) int

func PkgApiCall (x SomeFuncType) {
   ...
}

In my code using this package, I have some very similar:

type MyFuncType func (a interface{}, b interface{}) int

Now I want to call pkg1.PkgApiCall(), but with a variable of MyFuncType as argument:

package mypackage

func doingSomeThing(x MyFuncType) {
  pkg1.PkgApiCall(x)
}

It doesn't compile. I get the error

./src1.go:97:7: error: incompatible type in initialization (cannot use type mypackage.MyFuncType as type pkg1.SomeFuncType)

How could I get over this? These function types define functions with exactly the same signature.

The usual type conversions work for function types just as well as they work for non-function types:

pkg1.PkgApiCall(SomeFuncType(x))