sequence matters in return 1

    vars:
      tom: this is tom in global
      jerry: this is jerry in global
    tasks:
    - name: task
      desc: main entry
      task:
      - func: call
        desc: call subtask and exam the return value in following steps
        do: subtask1
      - func: cmd
        desc: |
          check value of tom
          in this case tom's value should come from subtask1
          tom's expected value:  tom created in subtask1
        do:
        - name: print
          cmd: 'in main task print3: {{.tom}}'
    - name: subtask1
      desc: subtask to test reg and return
      task:
      - func: cmd
        desc: check value of tom after it is registered in current task stack
        vars:
          john: john in sub_loop func1
        do:
        - name: reg
          desc: by default hitom is registered in to global context
          cmd:
            name: tom
            value: 'tom created in subtask1'
        - name: print
          cmd: 'in sub_loop print1: {{.tom}}'
      - func: cmd
        desc: check value of tom and it should be available in current stack
        vars:
          john: john in sub_loop func2
        do:
        - name: print
          cmd: 'in sub_loop print2: {{.tom}}'
        - name: return
          cmd:
          - tom
      - func: call
        desc: call subtask and exam the return value in following steps
        do: subtask2
    - name: subtask2
      desc: subtask to test reg and return
      task:
      - func: cmd
        desc: check value of tom after it is registered in current task stack
        vars:
          john: john in sub_loop func1
        do:
        - name: reg
          desc: by default hitom is registered in to global context
          cmd:
            name: tom
            value: 'tom2 created in subtask2'
        - name: print
          cmd: 'in sub_loop print1: {{.tom}}'
      - func: cmd
        desc: check value of tom and it should be available in current stack
        vars:
          john: john in sub_loop func2
        do:
        - name: print
          cmd: 'in sub_loop print2: {{.tom}}'
        - name: return
          cmd:
          - tom
    

    loading [Config]:  ./tests/functests/upconfig.yml
    Main config:
                 Version -> 1.0.0
                  RefDir -> ./tests/functests
                 WorkDir -> cwd
              AbsWorkDir -> /up_project/up
                TaskFile -> c0114
                 Verbose -> vvv
              ModuleName -> self
               ShellType -> /bin/sh
           MaxCallLayers -> 8
                 Timeout -> 3600000
     MaxModuelCallLayers -> 256
               EntryTask -> task
      ModRepoUsernameRef -> 
      ModRepoPasswordRef -> 
    work dir: /up_project/up
    -exec task: task
    loading [Task]:  ./tests/functests/c0114
    module: [self], instance id: [dev], exec profile: []
    profile -  envVars:
    
    (*core.Cache)({
    })
    
    Task1: [task ==> task: main entry ]
    -Step1: [: call subtask and exam the return value in following steps ]
    self: final context exec vars:
    
    (*core.Cache)({
      "jerry": "this is jerry in global",
      "tom": "this is tom in global",
      "up_runtime_task_layer_number": 0
    })
    
    =Task2: [task ==> subtask1: subtask to test reg and return ]
    --Step1: [: check value of tom after it is registered in current task stack ]
    self: final context exec vars:
    
    (*core.Cache)({
      "john": "john in sub_loop func1",
      "jerry": "this is jerry in global",
      "tom": "this is tom in global",
      "up_runtime_task_layer_number": 1
    })
    
    ~~SubStep1: [reg: by default hitom is registered in to global context ]
    ~~SubStep2: [print:  ]
    in sub_loop print1: tom created in subtask1
    --Step2: [: check value of tom and it should be available in current stack ]
    self: final context exec vars:
    
    (*core.Cache)({
      "john": "john in sub_loop func2",
      "jerry": "this is jerry in global",
      "tom": "tom created in subtask1",
      "up_runtime_task_layer_number": 1
    })
    
    ~~SubStep1: [print:  ]
    in sub_loop print2: tom created in subtask1
    ~~SubStep2: [return:  ]
    --Step3: [: call subtask and exam the return value in following steps ]
    self: final context exec vars:
    
    (*core.Cache)({
      "up_runtime_task_layer_number": 1,
      "jerry": "this is jerry in global",
      "tom": "tom created in subtask1"
    })
    
    ==Task3: [task/subtask1 ==> subtask2: subtask to test reg and return ]
    ---Step1: [: check value of tom after it is registered in current task stack ]
    self: final context exec vars:
    
    (*core.Cache)({
      "john": "john in sub_loop func1",
      "jerry": "this is jerry in global",
      "tom": "tom created in subtask1",
      "up_runtime_task_layer_number": 2
    })
    
    ~~~SubStep1: [reg: by default hitom is registered in to global context ]
    ~~~SubStep2: [print:  ]
    in sub_loop print1: tom2 created in subtask2
    ---Step2: [: check value of tom and it should be available in current stack ]
    self: final context exec vars:
    
    (*core.Cache)({
      "john": "john in sub_loop func2",
      "up_runtime_task_layer_number": 2,
      "jerry": "this is jerry in global",
      "tom": "tom2 created in subtask2"
    })
    
    ~~~SubStep1: [print:  ]
    in sub_loop print2: tom2 created in subtask2
    ~~~SubStep2: [return:  ]
    -Step2: [
    check value of tom
    in this case tom's value should come from subtask1
    tom's expected value:  tom created in subtask1
    ]
    self: final context exec vars:
    
    (*core.Cache)({
      "jerry": "this is jerry in global",
      "tom": "tom created in subtask1",
      "up_runtime_task_layer_number": 2
    })
    
    ~SubStep1: [print:  ]
    in main task print3: tom created in subtask1