Creating a flat array from the map entries in Go

What is the shortest (and idiomatic) way to create an array from the keys and values of a map w/o compromising on time complexity too much?

For instance, from the following map:

map[string]string { "1":"a", "2":"b" }

I need to create the following array:

[]string{"1","a", "2","b"}

I can do this in Scala with following:

val myMap = Map("1" -> "a", "2" -> "b")
myMap.keySet ++ myMap.values

Thank you.