Pure random data generator

rand.go

package main

import (
    "log"
    "net/http"
    "time"
    "math/rand"
    chart "github.com/wcharczuk/go-chart"
)

const SAMPLES = 200
const SCALE   = "24h"

func addData(ts *chart.TimeSeries, start time.Time, d time.Duration, samples int) {
    t := start
    r := rand.New(rand.NewSource(time.Now().UnixNano()))

    for i := 0; i < samples; i++ {
        ts.XValues = append(ts.XValues, t)
        ts.YValues = append(ts.YValues, r.Float64())
        t = t.Add(d)
    }
}

func drawChart(res http.ResponseWriter, req *http.Request) {
    var graph *chart.Chart
    var ts *chart.TimeSeries

    ts = &chart.TimeSeries{
        XValues: []time.Time{},
        YValues: []float64{},
    }
    graph = &chart.Chart{
        Series: []chart.Series{ts},
    }
    duration, _ := time.ParseDuration(SCALE)
    end := time.Now()
    start := end.Add(-duration)
    
    addData(ts, start, duration/SAMPLES, SAMPLES)
    if len(ts.XValues) == 0 {
        http.Error(res, "no data (yet)", http.StatusBadRequest)
        return
    }
    res.Header().Set("Content-Type", "image/png")
    if err := graph.Render(chart.PNG, res); err != nil {
        log.Printf("%v", err)
    }
}

func main() {
    http.HandleFunc("/", drawChart)
    log.Printf("Open http://localhost:8080\n")
    log.Fatal(http.ListenAndServe(":8080", nil))
}

go get -v
go run rand.go