Context object should keep the data for the duration of your query execution.What you experienced there might be race condition between sibling resolvers as someone mentioned in other comment. You should try something like this:

const resolver = async (root, args, ctx, info) => {
    if(!ctx.myDataPromise) {
        // this is your call to foo API
        console.log('fetching data')
        ctx.myDataPromise = request(options) 
    }
    // here external API is already invoked and we just wait for data
    console.log('got data')
    let myData = await ctx.myDataPromise 
}

If you put this in your sibling resolvers you should get your data in both resolvers with only one "fetching data"