Another approach would be using slices.Contains()

package main

import (
    "fmt"
    "slices"
)

type visit struct {
    x, y int
}

func main() {
    visited := []visit{
        visit{1, 100},
        visit{2, 2},
        visit{1, 100},
        visit{1, 1},
    }
    var unique []visit

    for _, i := range visited {
        skip := slices.Contains(unique, i)
        if !skip {
            unique = append(unique, i)
        }
    }

    fmt.Println(unique)
}