ng : File C:\Users\Lenovo\AppData\Roaming\npm\ng.ps1 cannot be loaded. The file C:\Users\Lenovo\AppData\Roaming\npm\ng.ps1 is not digitally signed. You cannot run this script on the current system. For more information about running scripts and setting execution policy, see about_Execution_Policies at https:/go.microsoft.com/fwlink/?LinkID=135170. At line:1 char:1

• ng serve
• ~~
  • CategoryInfo : SecurityError: (:) [], PSSecurityException
  • FullyQualifiedErrorId : UnauthorizedAccess

while giving ng serve showing this error..how to overcome it?

ng : File C:\Users\Lenovo\AppData\Roaming\npm\ng.ps1 cannot be loaded. The file C:\Users\Lenovo\AppData\Roaming\npm\ng.ps1 is not digitally signed. You cannot run 
this script on the current system. For more information about running scripts and setting execution policy, see about_Execution_Policies at 
https:/go.microsoft.com/fwlink/?LinkID=135170.
At line:1 char:1
+ ng serve
+ ~~
    + CategoryInfo          : SecurityError: (:) [], PSSecurityException
    + FullyQualifiedErrorId : UnauthorizedAccess

while giving ng serve showing this error..how to overcome it?