https://github.com/labstack/echo/pull/275

main.go

package main

import (
	"encoding/json"
	"math"
	"time"

	"github.com/labstack/echo"
	"github.com/labstack/gommon/log"
)

func NewErrorHandler() func(err error, ctx *echo.Context) {
	return func(err error, ctx *echo.Context) {
		log.Error("ErrorHandler: %T: %s (%s %s)", err, err, ctx.Request().Method, ctx.Request().RequestURI)

		if ctx.Response().Committed() {
			log.Error("ErrorHandler: response already commited!")
			return
		}

		ctx.JSON(500, map[string]string{"error": err.Error()})
	}
}

type (
	Geolocation struct {
		Altitude  float64
		Latitude  float64
		Longitude float64
	}
)

var (
	locations = []Geolocation{
		{-97, 37.819929, -122.478255},
		{1899, 39.096849, -120.032351},
		{2619, 37.865101, math.NaN()},
		{42, 33.812092, -117.918974},
		{15, 37.77493, -122.419416},
	}
)

func main() {
	e := echo.New()
	e.SetHTTPErrorHandler(NewErrorHandler())

	e.Get("/", func(c *echo.Context) error {
		c.Response().Header().Set(echo.ContentType, echo.ApplicationJSON)
		for _, l := range locations {
			if err := json.NewEncoder(c.Response()).Encode(l); err != nil {
				return err
			}
			c.Response().Flush()
			time.Sleep(1 * time.Second)
		}
		return nil
	})

	e.Run("127.0.0.1:1323")
}