title: How to allocate memory to map pointing to slice in golang
body: <p>Is there a way to allocate the memory of a map, which has at most <code>Nmax</code> keys, that points to a slice of maximum length <code>Nmax</code>? </p>
  
  <p>I'm currently just specifying the max number of keys via <code>make(map[int][]int,Nmax)</code>, but I'm not sure how to tell Go that each slice will be of maximum length <code>Nmax</code> because I don't know what the keys will be apriori.</p>
  
  <p>I essentially have a bunch of sites with an integer population. I use the map to keep track of how many sites have a given population <code>N</code>. The bottleneck in my program appears to be runtime.memmove, which I'm guessing comes from constant resizing of the slice the map points to. </p>