func (s *ProjectMembersService) DeleteProjectMember(pid interface{}, user int, options ...OptionFunc) (*Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, err
	}
	u := fmt.Sprintf("projects/%s/members/%d", url.QueryEscape(project), user)
	req, err := s.client.NewRequest("DELETE", u, nil, options)
	if err != nil {
		return nil, err
	}
	return s.client.Do(req, nil)
}
DeleteProjectMember removes a user from a project team.

GitLab API docs:
https://docs.gitlab.com/ce/api/members.html#remove-a-member-from-a-group-or-project
package gitlab
import (
	"fmt"
	"net/url"
)
type ProjectMembersService struct {
	client *Client
}
type ListProjectMembersOptions struct {
	ListOptions
	Query *string `url:"query,omitempty" json:"query,omitempty"`
}
func (s *ProjectMembersService) ListProjectMembers(pid interface{}, opt *ListProjectMembersOptions, options ...OptionFunc) ([]*ProjectMember, *Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, nil, err
	}
	u := fmt.Sprintf("projects/%s/members", url.QueryEscape(project))
	req, err := s.client.NewRequest("GET", u, opt, options)
	if err != nil {
		return nil, nil, err
	}
	var pm []*ProjectMember
	resp, err := s.client.Do(req, &pm)
	if err != nil {
		return nil, resp, err
	}
	return pm, resp, err
}
func (s *ProjectMembersService) GetProjectMember(pid interface{}, user int, options ...OptionFunc) (*ProjectMember, *Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, nil, err
	}
	u := fmt.Sprintf("projects/%s/members/%d", url.QueryEscape(project), user)
	req, err := s.client.NewRequest("GET", u, nil, options)
	if err != nil {
		return nil, nil, err
	}
	pm := new(ProjectMember)
	resp, err := s.client.Do(req, pm)
	if err != nil {
		return nil, resp, err
	}
	return pm, resp, err
}
type AddProjectMemberOptions struct {
	UserID      *int              `url:"user_id,omitempty" json:"user_id,omitempty"`
	AccessLevel *AccessLevelValue `url:"access_level,omitempty" json:"access_level,omitempty"`
}
func (s *ProjectMembersService) AddProjectMember(pid interface{}, opt *AddProjectMemberOptions, options ...OptionFunc) (*ProjectMember, *Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, nil, err
	}
	u := fmt.Sprintf("projects/%s/members", url.QueryEscape(project))
	req, err := s.client.NewRequest("POST", u, opt, options)
	if err != nil {
		return nil, nil, err
	}
	pm := new(ProjectMember)
	resp, err := s.client.Do(req, pm)
	if err != nil {
		return nil, resp, err
	}
	return pm, resp, err
}
type EditProjectMemberOptions struct {
	AccessLevel *AccessLevelValue `url:"access_level,omitempty" json:"access_level,omitempty"`
}
func (s *ProjectMembersService) EditProjectMember(pid interface{}, user int, opt *EditProjectMemberOptions, options ...OptionFunc) (*ProjectMember, *Response, error) {
	project, err := parseID(pid)
	if err != nil {
		return nil, nil, err
	}
	u := fmt.Sprintf("projects/%s/members/%d", url.QueryEscape(project), user)
	req, err := s.client.NewRequest("PUT", u, opt, options)
	if err != nil {
		return nil, nil, err
	}
	pm := new(ProjectMember)
	resp, err := s.client.Do(req, pm)
	if err != nil {
		return nil, resp, err
	}
	return pm, resp, err
}