You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: parser.go
    path of file: ./repos/faygo/vendor/gopkg.in/dgrijalva/jwt-go.v3
    
    the code of the file until where you have to start completion: package jwt

import (
	"bytes"
	"encoding/json"
	"fmt"
	"strings"
)

type Parser struct {
	ValidMethods         []string // If populated, only these methods will be considered valid
	UseJSONNumber        bool     // Use JSON Number format in JSON decoder
	SkipClaimsValidation bool     // Skip claims validation during token parsing
}

// Parse, validate, and return a token.
// keyFunc will receive the parsed token and should return the key for validating.
// If everything is kosher, err will be nil
func (p *Parser) Parse(tokenString string, keyFunc Keyfunc) (*Token, error) {
	return p.ParseWithClaims(tokenString, MapClaims{}, keyFunc)
}

func (p *Parser) ParseWithClaims(tokenString string, claims Claims, keyFunc Keyfunc) (*Token, error) {
	token, parts, err := p.ParseUnverified(tokenString, claims)
	if err != nil {
		return token, err
	}

	// Verify signing method is in the required set
	if p.ValidMethods != nil {
		var signingMethodValid = false
		var alg = token.Method.Alg()
		for _, m := range p.ValidMethods {
			if m == alg {
				signingMethodValid = true
				break
			}
		}
		if !signingMethodValid {
			// signing method is not in the listed set
			return token, NewValidationError(fmt.Sprintf("signing method %v is invalid", alg), ValidationErrorSignatureInvalid)
		}
	}

	// Lookup key
	var key interface{}
	if keyFunc == nil {
		// keyFunc was not provided.  short circuiting validation
		return token, NewValidationError("no Keyfunc was provided.", ValidationErrorUnverifiable)
	}
	if key, err = keyFunc(token); err != nil {
		// keyFunc returned an error
		if ve, ok := err.(*ValidationError); ok {
			return token, ve
		}
		return token, &ValidationError{Inner: err, Errors: Val
    
func (p *Parser) ParseWithClaims(tokenString string, claims Claims, keyFunc Keyfunc) (*Token, error) {
	token, parts, err := p.ParseUnverified(tokenString, claims)
	if err != nil {
		return token, err
	}

	// Verify signing method is in the required set
	if p.ValidMethods != nil {
		var signingMethodValid = false
		var alg = token.Method.Alg()
		for _, m := range p.ValidMethods {
			if m == alg {
				signingMethodValid = true
				break
			}
		}
		if !signingMethodValid {
			// signing method is not in the listed set
			return token, NewValidationError(fmt.Sprintf("signing method %v is invalid", alg), ValidationErrorSignatureInvalid)
		}
	}

	// Lookup key
	var key interface{}
	if keyFunc == nil {
		// keyFunc was not provided.  short circuiting validation
		return token, NewValidationError("no Keyfunc was provided.", ValidationErrorUnverifiable)
	}
	if key, err = keyFunc(token); err != nil {
		// keyFunc returned an error
		if ve, ok := err.(*ValidationError); ok {
			return token, ve
		}
		return token, &ValidationError{Inner: err, Errors: ValidationErrorUnverifiable}
	}

	vErr := &ValidationError{}

	// Validate Claims
	if !p.SkipClaimsValidation {
		if err := token.Claims.Valid(); err != nil {

			// If the Claims Valid returned an error, check if it is a validation error,
			// If it was another error type, create a ValidationError with a generic ClaimsInvalid flag set
			if e, ok := err.(*ValidationError); !ok {
				vErr = &ValidationError{Inner: err, Errors: ValidationErrorClaimsInvalid}
			} else {
				vErr = e
			}
		}
	}

	// Perform validation
	token.Signature = parts[2]
	if err = token.Method.Verify(strings.Join(parts[0:2], "."), token.Signature, key); err != nil {
		vErr.Inner = err
		vErr.Errors |= ValidationErrorSignatureInvalid
	}

	if vErr.valid() {
		token.Valid = true
		return token, nil
	}

	return token, vErr
}