Playing with Go data structures...

playing.go

package main

import (
	"fmt"
	"math/rand"
	"time"
)

type Cc struct {
	name string
	dep  int
	date time.Time
}

type Aux struct {
	accum int
	cant  int
}

func main() {
	var ccs []Cc
	horas := make(map[int]Aux)
	f1 := time.Now()
	for i := 0; i < 10; i++ {
		f1 = f1.Add(20 * time.Minute)
		ccs = append(ccs, Cc{name: "cespinoza", dep: rand.Intn(1000), date: f1})
	}
	for _, e := range ccs {
		for i := 0; i < 25; i++ {
			if e.date.Hour() == i {
				horas[i] = Aux{horas[i].accum + e.dep, horas[i].cant + 1 }
			}
		}
		fmt.Printf("%v %v %v\n", e.name, e.dep, e.date)
	}
	fmt.Println(horas)
}

Finally I'm getting ten records , maps with the value's sum for every hour and cantity, ready to average by hour:

hour:{sum values_cant}, ..