text: package strava
  
  import (
  	"encoding/json"
  	"errors"
  	"strings"
  	"time"
  
  	"github.com/markbates/goth"
  )
  
  // Session stores data during the auth process with Strava.
  type Session struct {
  	AuthURL      string
  	AccessToken  string
  	RefreshToken string
  	ExpiresAt    time.Time
  }
  
  // GetAuthURL will return the URL set by calling the `BeginAuth` function on the Strava provider.
  func (s Session) GetAuthURL() (string, error) {
  	if s.AuthURL == "" {
  		return "", errors.New(goth.NoAuthUrlErrorMessage)
  	}
  	return s.AuthURL, nil
  }
  
  // Authorize the session with Strava and return the access token to be stored for future use.
  func (s *Session) Authorize(provider goth.Provider, params goth.Params) (string, error) {
  	p := provider.(*Provider)
  	token, err := p.config.Exchange(goth.ContextForClient(p.Client()), params.Get("code"))
  	if err != nil {
  		return "", err
  	}
  
  	if !token.Valid() {
  		return "", errors.New("Invalid token received from provider")
  	}
  
  	s.AccessToken = token.AccessToken
  	s.RefreshToken = token.RefreshToken
  	s.ExpiresAt = token.Expiry
  	return token.AccessToken, err
  }
  
  // Marshal the session into a string
  func (s Session) Marshal() string {
  	b, _ := json.Marshal(s)
  	return string(b)
  }
  
  func (s Session) String() string {
  	return s.Marshal()
  }
  
  // UnmarshalSession will unmarshal a JSON string into a session.
  func (p *Provider) UnmarshalSession(data string) (goth.Session, error) {
  	s := &Session{}
  	err := json.NewDecoder(strings.NewReader(data)).Decode(s)
  	return s, err
  }
  