Unicity of complex key dictionaries in Go but not in Julia?

In GO when I use a struct as a key for a map, there is an unicity of the keys.

For example, the following code produce a map with only one key : map[{x 1}:1]

package main

import (
    "fmt"
)

type MyT struct {
    A string
    B int
}

func main() {

    dic := make(map[MyT]int)

    for i := 1; i <= 10; i++ {
        dic[MyT{"x", 1}] = 1
    }

    fmt.Println(dic)
}

// result : map[{x 1}:1]

I Tried to do the same in Julia and I had a strange surprise :

This Julia code, similar to the GO one, produces a dictionary whith 10 keys !

    type MyT
        A::String
        B::Int64
    end

    dic = Dict{MyT, Int64}()

    for i in 1:10
        dic[MyT("x", 1)] = 1
    end

    println(dic)
    # Dict(MyT("x",1)=>1,MyT("x",1)=>1,MyT("x",1)=>1,MyT("x",1)=>1,MyT("x",1)=>1,MyT("x",1)=>1,MyT("x",1)=>1,MyT("x",1)=>1,MyT("x",1)=>1,MyT("x",1)=>1)

    println(keys(dic))
    # MyT[MyT("x",1),MyT("x",1),MyT("x",1),MyT("x",1),MyT("x",1),MyT("x",1),MyT("x",1),MyT("x",1),MyT("x",1),MyT("x",1)]

So what I did wrong ?

Thank you @DanGetz for the solution ! :

immutable MyT     # or struct MyT with julia > 0.6
    A::String
    B::Int64
end

dic = Dict{MyT, Int64}()

for i in 1:10
    dic[MyT("x", 1)] = 1
end

println(dic)         # Dict(MyT("x", 1)=>1)
println(keys(dic))   # MyT[MyT("x", 1)]