golang: creating an instance requiring interface parameters...

endpoint.go

package mypackage

import (
	"net/http"

	"github.com/gobuffalo/buffalo"
	gateway "github.com/grpc-ecosystem/grpc-gateway/runtime"
	"github.com/pkg/errors"
	"github.com/prometheus/client_golang/api"
	"google.golang.org/grpc/status"
)

type PromRequest struct {
	Endpoint  string `json:"endpoint,omitempty"`
	Query     string `json:"query:omitempty"`
	TimeRange string `json:"timerange:omitempty"`
}

func getMetric(pr PromRequest) (*queryData, error) {
	apiConfig := api.Config{Address: pr.Endpoint} 
	promapi := api.NewClient(apiConfig)
}

func MetricsHandler(c buffalo.Context) error {
	var pr PromRequest
	var qd queryData

	endpoint := "http://myendpoint.domain.com/api/v1/"

	pr.Endpoint = endpoint
	pr.Query = c.Param("query")
	pr.TimeRange = c.Param("timerange")

	qd, err := getMetric(pr)
	if err != nil {
		return c.Error(gateway.HTTPStatusFromCode(status.Convert(err).Code()), errors.WithStack(err))
	}

	return c.Render(http.StatusOK, r.JSON(qd))
}

sigh. totally misread the docs.