func (s *PullRequestsService) ListComments(owner string, repo string, number int, opt *PullRequestListCommentsOptions) ([]PullRequestComment, *Response, error) {
	var u string
	if number == 0 {
		u = fmt.Sprintf("repos/%v/%v/pulls/comments", owner, repo)
	} else {
		u = fmt.Sprintf("repos/%v/%v/pulls/%d/comments", owner, repo, number)
	}
	u, err := addOptions(u, opt)
	if err != nil {
		return nil, nil, err
	}
	req, err := s.client.NewRequest("GET", u, nil)
	if err != nil {
		return nil, nil, err
	}
	comments := new([]PullRequestComment)
	resp, err := s.client.Do(req, comments)
	if err != nil {
		return nil, resp, err
	}
	return *comments, resp, err
}
ListComments lists all comments on the specified pull request.  Specifying a
pull request number of 0 will return all comments on all pull requests for
the repository.

GitHub API docs: https://developer.github.com/v3/pulls/comments/#list-comments-on-a-pull-request
package github
import (
	"fmt"
	"time"
)
type PullRequestComment struct {
	ID               *int       `json:"id,omitempty"`
	Body             *string    `json:"body,omitempty"`
	Path             *string    `json:"path,omitempty"`
	DiffHunk         *string    `json:"diff_hunk,omitempty"`
	Position         *int       `json:"position,omitempty"`
	OriginalPosition *int       `json:"original_position,omitempty"`
	CommitID         *string    `json:"commit_id,omitempty"`
	OriginalCommitID *string    `json:"original_commit_id,omitempty"`
	User             *User      `json:"user,omitempty"`
	CreatedAt        *time.Time `json:"created_at,omitempty"`
	UpdatedAt        *time.Time `json:"updated_at,omitempty"`
}
func (p PullRequestComment) String() string {
	return Stringify(p)
}
type PullRequestListCommentsOptions struct {
	Sort string `url:"sort,omitempty"`
	Direction string `url:"direction,omitempty"`
	Since time.Time `url:"since,omitempty"`
	ListOptions
}