How do I do table locking in GORM(Golang)?

You could use this code according to gorm.io docs:

Row-Level Lock Modes, FOR UPDATE

db.Clauses(clause.Locking{Strength: "UPDATE"}).Find(&users)
// SELECT * FROM `users` FOR UPDATE

Also, you could use other lock mode instead of UPDATE, like: KEY SHARE, SHARE, NO KEY UPDATE.

Table-Level Lock Modes

For locking a table, as far as I can see there is no option with Gorm right now, because Gorm always put FOR, when merging Clauses. but you can use a raw query to achieve what you want:

db.Exec("LOCK TABLE table_name_here IN ACCESS EXCLUSIVE MODE")

// LOCK [ TABLE ] [ ONLY ] name [ * ] [, ...] [ IN lockmode MODE ] [ NOWAIT ]

where lockmode is one of:

ACCESS SHARE | ROW SHARE | ROW EXCLUSIVE | SHARE UPDATE EXCLUSIVE
| SHARE | SHARE ROW EXCLUSIVE | EXCLUSIVE | ACCESS EXCLUSIVE

More info on Postgres locks here

Add options

You can use Options to add any option that you want, this will be appear after the Strength.

db.Clauses(clause.Locking{
  Strength: "UPDATE",
  Options: "NOWAIT",
}).Find(&users)
// SELECT * FROM `users` FOR UPDATE NOWAIT