func (s *OrganizationsService) IsPublicMember(org, user string) (bool, *Response, error) {
	u := fmt.Sprintf("orgs/%v/public_members/%v", org, user)
	req, err := s.client.NewRequest("GET", u, nil)
	if err != nil {
		return false, nil, err
	}
	resp, err := s.client.Do(req, nil)
	member, err := parseBoolResponse(err)
	return member, resp, err
}
IsPublicMember checks if a user is a public member of an organization.

GitHub API docs: http://developer.github.com/v3/orgs/members/#check-public-membership
package github
import "fmt"
type Membership struct {
	URL *string `json:"url,omitempty"`
	State *string `json:"state,omitempty"`
	Role *string `json:"role,omitempty"`
	OrganizationURL *string `json:"organization_url,omitempty"`
	Organization *Organization `json:"organization,omitempty"`
	User *User `json:"user,omitempty"`
}
func (m Membership) String() string {
	return Stringify(m)
}
type ListMembersOptions struct {
	PublicOnly bool `url:"-"`
	Filter string `url:"filter,omitempty"`
	Role string `url:"role,omitempty"`
	ListOptions
}
func (s *OrganizationsService) ListMembers(org string, opt *ListMembersOptions) ([]User, *Response, error) {
	var u string
	if opt != nil && opt.PublicOnly {
		u = fmt.Sprintf("orgs/%v/public_members", org)
	} else {
		u = fmt.Sprintf("orgs/%v/members", org)
	}
	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
	}
	if opt != nil && opt.Role != "" {
		req.Header.Set("Accept", mediaTypeOrgPermissionPreview)
	}
	members := new([]User)
	resp, err := s.client.Do(req, members)
	if err != nil {
		return nil, resp, err
	}
	return *members, resp, err
}
func (s *OrganizationsService) IsMember(org, user string) (bool, *Response, error) {
	u := fmt.Sprintf("orgs/%v/members/%v", org, user)
	req, err := s.client.NewRequest("GET", u, nil)
	if err != nil {
		return false, nil, err
	}
	resp, err := s.client.Do(req, nil)
	member, err := parseBoolResponse(err)
	return member, resp, err
}