gopg: exclude column when upserting records

[v36372]

This will update all fields

db.Model(&models).OnConflict("(conflicted_fields) DO UPDATE").Insert()

This will update the specified fields

db.Model(&models).
    OnConflict("(conflicted_fields) DO UPDATE").
    Set("models.a = EXCLUDED.a"). 
    Insert()

This will update all fields except a

db.Model(&models).
    OnConflict("(conflicted_fields) DO UPDATE").
    ExcludeColumn("a").
    Insert()