Want to add new column from string but df[!,field_in] = "test" not working

[pdeffebach]

Make it a vector.

julia> df = DataFrame()
0×0 DataFrame

julia> df[!,field_in] =  [payload]
1-element Vector{String}:
 "new_one"

julia> df
1×1 DataFrame
 Row │ top_level 
     │ String    
─────┼───────────
   1 │ new_one