golang是否有支持集合数据结构的计划？

This feature can be implemented with 'map'.

countrySet := map[string]bool{
  "US": true,
  "JP": true, 
  "KR": true,
}

But to ease the eyes of readers, 'set' is a necessary data structure.

countrySet := set[string]{"US", "JP", "KR"}

Or init 'map' with keys only. For example:

countrySet := map[string]bool{"US", "JP", "KR"}

Does golang have the plan for supporting syntax like this?

I don't know about such plans.

What you may do to ease the initialization:

Use a one-letter bool constant:

const t = true
countrySet := map[string]bool{"US": t, "JP": t, "KR": t}

Use a loop to add the keys, so you only need to list the keys:

countrySet := map[string]bool{}
for _, v := range []string{"US", "JP", "KR"} {
    countrySet[v] = true
}

This is only profitable if you have more elements.

But you can always create a helper function:

func createSet(es ...string) map[string]bool {
    m := map[string]bool{}
    for _, v := range es {
        m[v] = true
    }
    return m
}

And then using it:

countrySet := createSet("US", "JP", "KR")

The plan is not to support everything in the Go standard library. The plan is to encourage open source, independently developed packages. For example, one of many,

package sets

import "k8s.io/apimachinery/pkg/util/sets"

Package sets has auto-generated set types.