package main

import "fmt"

type MyType interface {
    int | int8 | int16 | int32 | int64 | uint | uint8 | uint16 | uint32 | uint64 | string
}

func Unique[T MyType](m []T) []T {
    var k2 int
    un := []T{}
    for k1, v1 := range m {
        for k2 = 0; k2 < k1 && v1 != m[k2]; k2++ {
        }
        if k1 == k2 || v1 != m[k2] {
            un = append(un, v1)
        }
    }
    return un
}

func main() {
    input := []string{"green", "red", "green", "blue", "red"}
    unique := Unique(input)
    fmt.Println(unique)
}

Playground