How to change input value in formly?

Question

I want to append "}"(curly braces) to model property_name given by the user .

                                   key: 'property_name',
                                   type: 'input',
                                   templateOptions: {
                                       type:'text',
                                       label: 'property name',
                                       required : true
                                   },

for example: if user type "star" then "star }" will go to backend.