How to shutdown daemon completely in code or clear the memory of it.

Version/Platform/Processor information (from `ipfs version --all`):ipfs version --all

Type (bug, feature, meta, test failure, question):feature
Area (api, commands, daemon, fuse, etc):daemon
Priority (from P0: functioning, to P4: operations on fire):P3

Description:
I have integrated ipfs to mobile client by modifying the main entry to api mode.Now I have to shutdown damon,because ios will suspend the app after it enters background several minutes and ipfs will not work on entering foreground. I get the IpfsNode on daemonfunc,call IpfsNode.close() to close daemon,daemon will return,and I can retart daemon.But the memory will increase after retart daemon everytime. So I want to find methods to shutdown daemon completely,and can reduce the memory of ipfs.