Store map key/values in a persistent file

I will be creating a structure more or less of the form:

type FileState struct {
    LastModified int64
    Hash string
    Path string
}

I want to write these values to a file and read them in on subsequent calls. My initial plan is to read them into a map and lookup values (Hash and LastModified) using the key (Path). Is there a slick way of doing this in Go?

If not, what file format can you recommend? I have read about and experimented with with some key/value file stores in previous projects, but not using Go. Right now, my requirements are probably fairly simple so a big database server system would be overkill. I just want something I can write to and read from quickly, easily, and portably (Windows, Mac, Linux). Because I have to deploy on multiple platforms I am trying to keep my non-go dependencies to a minimum.

I've considered XML, CSV, JSON. I've briefly looked at the gob package in Go and noticed a BSON package on the Go package dashboard, but I'm not sure if those apply.

My primary goal here is to get up and running quickly, which means the least amount of code I need to write along with ease of deployment.